Idiot's guide to Subtractive Synthesis Pt 1

jtsuited

Everything you need to know for Subtractive Synthesis

First off, I’m not going to do it on any particular synthesizer. All subtractive synthesiser work in pretty much the same way. If you can use one, you should be able to use them all ONCE you understand exactly how a subtractive synthesizer works.
But for learning I reckon one of the best synths to learn on is the Arturia Moog Modular V, as you can actually see the signal paths because of the cables. I learnt everything on this softsynth and getting to grips with any other softsynth literally only takes a minute or two because the modular environment gives you a completely thorough understanding.

Or something simple like a minimoog emulator. But since you’ll have to pay for or steal most of these, I’d advise you start with something like the TAL UNO 62 or something free like that. The advantage of this is that it sounds fairly terrible unless you really know what you’re doing. And there’s only a rudimentary chorus to polish it with. So it forces you to work the sound. Anywho, on to the Basics.....

The Basics
What is subtractive synthesis?
This is easy.....Subtractive synthesis is merely making a sound by generating a signal and passing it through a filter.......
That’s all it is.

There are bells and whistles on every synthesizer to make this process interesting but fundamentally that’s all there is to it.

So what ‘signal’ are you talking about? Glad you asked.......because now we can start learning about.....Oscillators and Noise Generators

Oscillators and Noise Generators

Ok without sounding facetious, an oscillator oscillates. It generates a waveform that has many characteristics, some of whom are vital to understand for the purpose of synthesis.....

1. Frequency - how many cycles of the wave happen in a specific time determines the pitch. 440 cycles per second is what we call on the piano A. All pitch is, is the frequency (for the sake of learning synthesis).

2. Amplitude - how big the wave is. for simplicity purposes....amplitude = loudness or strength of signal

3. Shape - Ah here’s the good stuff.....let’s go through some waveshapes....

Sine - The smooth looking one. Only creates the fundamental frequency with no harmonics. So if we play a sine wave at 440 cycles per second (hz) , we hear concert A. No overtones, no nothing, just the note of A.

Saw - The saw shaped one. Creates the fundamental frequency AND both odd and even harmonics (don’t worry you don’t really need to understand the difference in sound between odd and even harmonics- you’ll hear them).

Square - The square shaped one. Creates only odd integer harmonics (don’t worry, just bear with me if you don’t know what that means)

Triangle Wave - Only contains odd harmonics like the square wave but they roll off (if you are still reading intently, god bless your attention because I’m boring myself here) as you go up.

Pulse Wave - This is a cool one because it’s like a square wave but it’s not symmetrical. Well actually the cool thing is, we’re able to alter the shape of this wave over time in a synthesizer using a thing called pulse-width-modulation (pwm), in which we er, modulate the width of the pulse.


Also you can have in the oscillator section of a synthesiser a noise generator. I’m not gonna explain the differences between White Noise, Brown Noise, Pink Noise and Gaussian noise, because all you need to know is that noise (in the context of a synthesizer) is every harmonic at equal amplitude. It’s like playing every note at the one time from 0hz - 20khz.

Right think that’s the oscillator section done.....

Filters
Filters are the subtractor that is referred to in subtractive synthesis, they just subtract bits from the sound. A low pass filter only lets frequencies below a certain point through. A hi pass does the opposite. Band pass sort of does both.

Now filters naturally resonate slightly at the point specified where you want it to roll off. Don’t ask why, they just do. So there’s a little bump at the frequency you specify. Thankfully, this little bump sounds friggin awesome. So awesome that nearly ever filter will have a resonance level so you can turn this bump right up to the point of self oscillation (the acid bass sound is the sound of the TB-303’s filter self oscillating), or you can be all boring and leave the resonance at a minimum.
In the context of band pass filtering it’s actually called bandwidth (how wide your bump is). At the end of the day band pass filtering is just one big bump with slopes on either side.

All Easy So Far?
Good because that’s the main stuff done. That’s the bread and butter out of the way.
But there is one more bit to it..... Modulation

Modulation
Modulating means changing (in the context of this terribly rough guide). We can chage pretty much everything we’ve discussed so far - we can modulate the amplitude of the signal, the frequency of the filters, the pitch of the oscillators, yadda yadda yadda... you name it, we can probably modulate it.

We modulate these things using mainly two things (one of which we’ve covered already -huzzah!) - oscillators and envelope generators.

Oscillators
Yup, just like when we’re using to oscillator to create sound, we can use them to simply control parameters on a different thing eg. the filter cutoff point, the pitch of the main oscillator, the amplitude, etc.

Mainly we use oscillators that are ‘going’ quite slow. As in they’re only cycling a few times a second. As you clever lads have figured out, that would mean they’re operating at a very low frequency. And hence the reason that for modulation purposes we use a special type of osciallator called a Low Frequency Oscillator. Or LFO.

Envelope Generators
Now this is the new bit. The most common type of modulation envelope we use is called an ADSR. This acronym is formed by the 4 different controls we have on the Envelope Generator (from here on in, just referred to as the Envelope). They are

Attack - How quickly the envelope reaches it’s peak
Decay - How long it takes for the initial peak to die off
Sustain - The LEVEL (very important to remember that) that is generated as long as a key is depressed. (if you haven’t watched Spinal Tap, and you haven’t seen the famous Les Paul scene, go watch it now, even though technically what Nigel is referring to is the release)
Release - How long the end of the envelope takes to die off.

ADSR’s couldn’t be simpler but if you can’t envisage how they work, google image ADSR and I’m sure it will instantly make sense.

So er, how does this all work in a synthesiser. Well you have two main types of envelopes in a synth. The Amplitude Envelope and the Filter Envelope.
The Amplitude envelope is what gives the overall amplitude of the sound it’s time-based characteristics.
A percussive sound will have a quick attack (close to 0), a short decay, no sustain, and a little or no release.
A lush pad sound will fade in slowly with a long attack, not much decay, nearly full sustain, and nice bit of release to let it hang a little.

So you get the point regarding amp envelopes.

Then you have the envelope that’s controlling the filter. Here what you are doing is giving a little shape for the cutoff to follow everytime you hit a key. Obviously this is going to effect the timbre of the sound over time.

Now before we go any further I want you to know that EVERYTHING on a subtractive synthesizer is modulatable (not sure if that’s a word). Some synths let you modulate feck all. Some let you modulate everything. But you’ll learn in due course what synths facilitate what.
Synth Programming
The good stuff..... Now if you understand what I’ve written so far, it’s time to get stuck in and you’ll soon see why presets are the devil, and how simple all this is ONCE you understand the fundamentals.

Now for ease of use, we’re gonna do a little practical exercise. Pull out the TAL UNO - 62 synth and open it up on it’s init patch. These ‘init’ patches on all synths tend to just be a raw oscillator going into an open filter with full sustain on the amplitude envelope. And for good reason. It means it’s the perfect starting point because it’s here you gotta get a suitable oscillator sound.

Now if your init patch is the same as mine, you’re gonna get a dodgy sounding mix of saw and square wave (which will be an octave down), and it’s gonna sound rubbish.

So first thing we’re going to do is get some nice sound coming out of the oscillator. So, turn off the saw and the square sub, and turn on the oscillator on the left. This is the pulse wave and what we’re going to do is modulate the pulse width with an LFO.

So give a little nudge to the PWM fader, and start adjusting the LFO rate. The sound will start moving and becoming a little bit richer and more refined. Feel free to adjust the delay time on the LFO so it fades in.

Fiddle a little until it starts sounding all rich and analogue-y and sort of Aphex-y, and basically interesting.

Now, just as an aside. Many softsynths have impressive presets but are crap to start from scratch from.....why? Because putting it bluntly they’re oscillators have no raw charm. The synth might have incredible modulation abilities but it’s starting off with a crap source. Personally I find most softsynths which aren’t emulations of classic gear tend to have very cold an uninspiring oscillators, and well, garbage in- garbage out in my humble opinion.

But anywho on to the filters. Close the Low Pass Filter completely and push the ENV modulation amount up to about half way. It’s time to start sculpting the sound.

Now on this particular synth, the Amplitude and Filter are modulated by the same envelope so we’re somewhat limited, but as you’ll see you can still get some lovely sounds out of it.

BTW, make sure to set the button to the left of the ADSR to env and not gate.

Now, I’ve got some retro chords going on with this sound and I’m gonna shape a bit more with the ADSR by giving a slow attack, no decay, full sustain and lots of release.

Now is the time to start tweaking and experimenting and seeing what you can get out of this with quite limited modulation capabilities.

At this stage we’ve got a bit of starting point for our pad sound. It’s all sounding a bit too much ‘Switched on Bach’ but when you start getting stuck in here, you’ll see why a whole generation of musicians have spent half their lives tweaking knobs. The fun really begins.

This stage you come to in your synthesis career is what I like to call the arrival. You know exactly how a synthesizer works, you’re about to find out what little adjustments here and there do, but most importantly you’re starting from a blank canvas with your sounds. If you always follow the start from scratch principle of a raw oscillator into a an open filter you will quickly learn how to synthesize certain instruments.

For those of you interested, a glockenspiel or marimba or anything from that family of instruments is easily done with a collection of sine waves and triangle waves tuned semi-inharmonically. I will do a full glock later on if you’re interested.

Anywho lads, hope someone learned something.

seannash

Copied into the ever expanding "Tips from Jeff" folder on my harddrive:)

Cheers dude

red dave

class jt, will have a proper read through this from home.

much appreciated

romarr

jtsuited wrote: »

So what ‘signal’ are you talking about? Glad you asked.......because now we can start learning about.....Oscillators and Noise Generators

at this point I had an image of JT in jacket, leather elbow patches, little pointing stick, in a haze of chalk dust ... something like JT meets prof Weeto !

good work ! cheers

jtsuited

far more accurate to imagine me, surrounded by records our of their sleeves, fag in mouth, sleep deprived trying to finish off a dubstep/UK funky EP, while using my hour break to talk sh1te on the internet!!

Imagine Shane Mac Gowan crossed with.....actually just Mac Gowan.

dasdog

Really excellent post. This would consist of a few classes of a module in a sound engineering course.

jtsuited

anyone know anything free and easy that lets you draw little schematics or circuit diagrams??

edit: all the schematics i'm finding on the internet complicate the whole thing far too much with their proper layout and correct labelling.

jtsuited

btw let me know how y'all get on with that little exercise. If you're completely new and clueless I envy you. Because once synthesis clicks it's a HUGE eureka moment. Every synthesizer is easy to program from scratch, and the fun begins.

Importantly and I didn't mention it in the OP, the real advantage of doing things this way is the reverse engineering part. When you hear a killer sound on a record, you're able to figure out exactly how they did it because you'll be able to hear ' ah yeah that's a pulse wave with a tight filter on it, loads of resonance and a short decay on the filter envelope but long one on the amp env, etc. etc. '

Elevator

thanks for this Jeff, I'm currently starting out after completing a level 5 fetac music tech course last year and this is defo going down as one of the best tutorials i've seen for this subject

I learned a lot and can't wait to go and put it into practice

which daws you using?

Neurojazz

Nice tutorial.

When ever i meet a piece of software or hardware i strip off and disable all the filters, fx and anything that is in the path of the raw source wave to see how the synth sounds on it's own.

A guy in a shop got very narked when i went around the back of his keyboard rack and asked him to turn off the tube processor rackmount he's put on his waldorf on sale to try and make it sound warmer than the cheaper roland above it.

The source of something like an mc202 or sh101 is something else to hear compared to a massive waldorf offering a million knobs and lfo - so always worth checking.

jtsuited

Elevator wrote: »

which daws you using?

Logic

krd

jtsuited, thanks for the tutorial - and the glock.

I need this - my sounds are depressingly bad. I think I have ear fatigue - or ear mold at the minute.

jtsuited

Neurojazz wrote: »

Nice tutorial.

When ever i meet a piece of software or hardware i strip off and disable all the filters, fx and anything that is in the path of the raw source wave to see how the synth sounds on it's own.

A guy in a shop got very narked when i went around the back of his keyboard rack and asked him to turn off the tube processor rackmount he's put on his waldorf on sale to try and make it sound warmer than the cheaper roland above it.

The source of something like an mc202 or sh101 is something else to hear compared to a massive waldorf offering a million knobs and lfo - so always worth checking.

well this is it isn't it. a lot of the older more restrictive limited synths really only had nice oscillators and filters. hence the reason their soft synth counterparts get those things right.

jose-fahartose

Nice tutorial Jeff, really well written

Sky King

An idiot's guide to music theory should be the sequel, methinks!

Sky King

Yesh. i am bored. Bear in mind I am self-taught so if there's any aficianados here, feel free to correct me n stuff I got slightly wrong or didnt explain well.

I am using the word 'piano' as opposed to keyboard in case people are dense enough to press the C key on their computers keyboard! It's all the same anyway.


The Piano
There are 12 keys in an octave on your piano/ keyboard /synth /pipe organ / harpsichord . 7 white and 5 black. The pattern repeats itself, all the way up the keyboard.

We generally take C as a starting point when learning. If you don't know which key this is on your piano, google it. I learned it by remembering that it was to the immediate left of two black keys, which looked like chopsticks... c is for chopsticks yeah? Or am I a saddo?

Eh, anyway as you press all the white and black keys in sequence, you are increasing in intrevals known as semitones, for example if you press C then you press the black key to the immediate right of it (C sharp) that is an interval of one semitone.

(Your synth may have a transpose dial and that will pitch your notation up or down and this is generally in semitone increments)

Once you press all 12 notes, the 13th note is C again, so don't be daunted by all the notes on the piano, there's only 12.

Also if you like a melody you have written but want it in a lower register, turning the transpose dial down by -12st brings all the notes lower by one octave but stays in the same key!

This is the same as selecting all the midi notes and dragging them down 12 semitones.


Scales and keys
You often hear of people saying 'what key is that music in' or 'he is singing out of key'. Music is generally written in a particular key... for example the key of C major is all the white keys on your keyboard, starting on C... the root note.

If you press all the white keys sequentially, you'll be going CDEFGAB and then back to C again. The full scale of C major. It's a familiar sound, we've all done it!

You'll notice as you play the scale that sometimes you skip a semitone and sometimes not (i.e. when you go from E to F). All major scales follow the same pattern of whole tones and semitones.

whole-whole-semi-whole-whole-whole-semi

So if you pick any key onthe piano at random and apply this rule, you'll play the major scale for that key

LEARN THEM OFF!!! There's only 12. IT'S A PAIN IN THE A-HOLE BUT TOTALLY WORTH IT.

Minor scales also have their own pattern, but luckily for you, every major scale has a relative minor. For example all the white keys on the piano starting with A is the key of A minor. This means that A is the relative minor of C... capiche?

It follows that the 6th note of every major scale is the starting point for its relative minor. So once you have the major ones learnt, the minors should be easy peasy lemon squeezy.

The order in which to learn them should be in the number of sharps/flats in the key (don't worry about why). C major has none. G major has one. D major has two and so on.

Notice that if you count five notes up the key of C major you arrive at G... then if you count five notes up the key of G you arrive at D... this is explained graphically inthe circle of fifths chart which makes it very easy to understand and also displays the relative minor keys:

http://en.wikipedia.org/wiki/Circle_of_fifths


Chords
So you've gone off and learnt all your major and minor scales off. Good man. Now you're ready to spice it up with some chords.

So what is a chord? well basically it is a collection of notes in a particular key. There's lots of different combinations of what is essentially the same thing, the most straightforward are triads.

A triad is the 1st, 3rd, and 5th notes of a scale played simultaneously to form a chord.

Look at your piano and do that.... press C E and G. That is the chord of C major. Moving up the white keys, press D F and A. That's the chord of D minor. Work your way up the scale and hey presto, you can play all the main chords in the key of C major (and of course its relative minor, A minor, as we discussed)

The chords in a key are given roman numerals I and II and III and IV etc.... for first degree second degree and so forth.

You will find that lots of music (especially pop music) follows patterns of chords. These are called chord progressions. For example, it might go I , IV, V . You know when a song 'feels right?'... familiar like youve heard it before even though you havent? chances are you've heard that progression a thousand times before.

Chords are very important to colour your music and give it emotion. major chords are often thought of as being bright and happy sounding, minor tend to sound sadder.

Without them it can sound bland and lifeless, and a simple three chord progression can transform your music, really bring out a bassline or compliment a vocal track.

This stuff is all over the internet, and should be learned to make life easier when composing. It's a vital tool for the job, if you like.

You might think you don't need theory, but you could sit down at your synth and spend 3 hours working out for yourself what is essentially a I V IV chord progression that a theory head could have shown you in 1 minute.

Questions or comments?

red dave

kilkenny flyer wrote: »

I am using the word 'piano' as opposed to keyboard in case people are dense enough to press the C key on their computers keyboard!

haha

Thanks a million for that, just having a quick gander at it. It really is about putting the time in to learn these basics that will pay dividends in the long run.

I had printed off pages from this site for the first few remix competitions. However crash course learning wasn't happening (time-wise). Have to set aside time after these remix things to drill these basics into my head.

jtsuited

I'm one of the aficianados (to an extent) that you're talking about Flyer, and what you have up there is probably the most easy to understand, yet thorough, and concise guide to the basics of music theory.

Fair play dude. Worthy of it's own thread definitely.

Sky King

Cheers m8

I was thinking of doing a 10 minute youtube video along the lines of 'Music Theory for Budding Producers' with this stuff, and a few clips of how a chord progression can completely transform a song.

It's hard to write down how something sounds!

Standman

There's a pretty decent book I picked up recently called "The Dance Music Manual" that has info on everything from basic music theory, synth programming, mixing and mastering to sample clearance and promoting your self as a DJ.

It's fairly comprehensive, has a lot of illustrations/diagrams and the like and also comes with a CD with various VST's and audio examples of methods and sounds discussed in the book. It's quite handy to get a grasp on a lot of the basics and you have all the information in one place. Here's the Amazon link if anyones interested, you can use the "look inside" function to read a lot of the book online!

acman

Nice one JT, thanks!

On a similar note (oh no he didn't!), I found this article really helpful too:

How Subtractive Synthesizers Work

electrogrimey

Thought I'd add in a few nice chord progressions to tack onto the end of that very eloquent explanation of theory. These are all common progressions in 'Bach-style' harmony, which is basically normal Western harmony, i.e., it'll all sound 'nice'.

When using roman numerals to describe chords, capitals are major, small letters are minor. Without a letter it is the root of the chord, so I, in C Major., is just a C chord. You use letters to describe the inversion of the chord. Ib will be a C chord with an E as the base of the chord, and Ic will be a C with a G as the base of the chord. Inversions change the sound of a progression a huge amount.

V7 is a dominant 7th chord, so in C major, V7 will be a G7. V7d will be a G7 with an F in the bass.

Major:

ii - V - I (basically the most common sequence in Western music)

iv - ii -V - I (little extension of that)

I - iv - ii - V - I (again)

vi - IV (any chord progression dropping a third is great)

I - vi - IV - ii (with above logic)

I - vi - IV - ii - V - I (adding point 1 and point 2 together)

Basically any combination of I, IV, and V. You can't go wrong.

V - vi (you'll recognize the sound, interrupted cadence)

V7d - Ib (personal favourite of mine)

Minor:

Basically all the above progressions and cadences are applicable in minor as well. They work equally well. IV will be a minor chord in minor though, and vi will be major, and of course I will be minor. V is still major.

Also, ivb - V is beautiful in minor. Use it if you can.

Tips for richer harmonies:

If you want richer harmonies in your stabs or whatever:

1) Always have a root, fifth, and third in your chord.
2) When doubling notes, double the root first. A doubled fifth/third without a doubled root will sound weaker.
3)When changing chords try to have the individual notes moving no more than a 3rd.

That's all I can think of for now.

seannash

Can we sticky these informative posts from Jeff,Flyer and Grimey please

jtsuited

haha, people are gonna sit down and learn grimey's post, and then everytime the radio comes on are just gonna facepalm immediately as the same sh1t pops up over and over again. It's like finding out about Santa.

jtsuited

oh and can we amend grimey's post with...

If you wanna sound black put a 7th into every chord you play....every one of them..

If you wanna sound black and from detroit....add the 9th too. M7add9 ftw

electrogrimey

I imagine (something I've yet to try) you could get more interesting lead lines by thinking about them harmonically. Write the bassline, matching the chords to that, and then make the bones of the lead line out of the most harmonically interesting notes in the chords.

Something that I left out, for stuff like held synth notes for build-ups etc, the fifth of the root chord is generally the best (a G in C major). I think people like Swedish House Mafia will, along with a white noise track that rises in volume and drops at each break, have a line that does the same volume-wise, with just a held synth note of the root of the 5th. It's because chord V needs to resolve to the I, so if it's not resolved, it builds suspense.

The 7th of chord V, or the leading note of the scale would also do the trick, but they're both less likely to work harmonically over changing chords.

jtsuited

I'm absolutely ashamed to say, my brain switches off when it comes to theory. I learnt it so young that I've never had to think about it linguistically.

Although learning jazz drums and piano I did have to push myself back into the habit of looking at the feckin sheet music. Not for jazz bass though, found a deadly book that had this awesome cd, so you could throw away the book, practice your turnarounds all night jamming along to this cd with a spliff in your mouth. Conk out on the couch and when you woke up you were a real life Jaco Pastorius.

electrogrimey

To get this back to subtractive synthesis, does anyone feel like putting up a few formulae for standard sounds as a basis for messing around with? (i.e. 'sine wave + small decay and no sustain = stab sound' kind of thing)

jtsuited

was gonna do that in part 2

red dave

If this is ever stickied, it should have the title "bible of music production" as its heading. Thanks to all for these vital basics

Sky King

I get the impression JT and grimey are at this theory business for donkey's years.

Myself, not so long, although I am drumming since I was a kid I only learnt theory bit as an adult and can empathise with anyone pulling their hair out over this stuff!

You may not know what grimey means by a chord inversion. It just means hitting the same notes in the chord but re-arranging the order.

Like a C major chord is C E and G right? With C as the lowest note in the chord. Well take that low C out and stick in the C from the octave above it instead.

Chord sounds slightly different, even though it's essentially the same thing. That's the first inversion. Carry this on through for the E and that's the second.

They're fun to mess around with.