Synthesis Question

jiltloop

Hi guys, I just have a synthesis question and hope someone can explain it to me. I know a fair bit about subtractive synthesis and I'd consider myself fairly strong on the theory of it but one thing I have come across a couple of times recently is sample and hold. Can someone explain to me what sample and hold is all about and how it fits into programming a sound? Thanks in advance.

PMI

Any good to ya??

http://www.soundonsound.com/sos/aug00/articles/synthsec.htm

jiltloop

That's the ticket cheers PMI. I forgot about checking out sound on sound.

Valcin

Hey Jiltloop,

I'm far from an expert but my understanding of Sample and Hold is that its a random LFO. On a lot of synths there are 4 different types of LFO: Triangle, Square, Saw and Sample and Hold(or Random wave). If you had an LFO assigned to say the Amp Volume, the triangle one would make the volume rise and fall at the speed of the LFO, a square wave would give intermitant volume while the Sample and Hold would give it a random volume where by the volume would shift all over the place at the speed of the LFO. If assigned to the frequency, the triangle LFO will make the pitch rise and fall while the Sample and Hold LFO will make random notes all over the place. If that makes any sense.

I'm not sure about this but I think an example of a sample and Hold LFO is the main riff out of Underworld's Rez:
http://www.youtube.com/watch?v=a6XOuiqW0WI&feature=related

I think its a Sample and Hold LFO assigned to modulate the frequency(or maybe its to the filter and its the resonance that is making the random notes?). There is constant random notes in the main riff. I've gotten similar sounds from sample and hold LFO's on my synths. If they did do that riff that way they kind of fluked one of the greatest riffs in dance. They probably recorded ages of random notes and heard that savage riff somewhere in the middle and then sampled it and looped it. Great bunch of lads


Edit: Just double checked there now on my Evolver Synth. Something like the Rez main riff can be got by taking a plain bass sound with no modulation and put some distortion on it, then put a Sample and Hold(may be called Random on your synth) LFO destined to the the Low Pass Filter. Put the resonance up high and put your Low pass Filter low. Keep the LFO frequency or maybe called speed on your synth at mid level. Then just hold down one note on your keyboard and you'll get squelchy Rez sh!t. The same should apply to any other synth with a Sample and Hold(again it maybe called Random on your synth) LFO.

jiltloop

Valcin wrote: »

Hey Jiltloop,

I'm far from an expert but my understanding of Sample and Hold is that its a random LFO. On a lot of synths there are 4 different types of LFO: Triangle, Square, Saw and Sample and Hold(or Random wave). If you had an LFO assigned to say the Amp Volume, the triangle one would make the volume rise and fall at the speed of the LFO, a square wave would give intermitant volume while the Sample and Hold would give it a random volume where by the volume would shift all over the place at the speed of the LFO. If assigned to the frequency, the triangle LFO will make the pitch rise and fall while the Sample and Hold LFO will make random notes all over the place. If that makes any sense.

I'm not sure about this but I think an example of a sample and Hold LFO is the main riff out of Underworld's Rez:
http://www.youtube.com/watch?v=a6XOuiqW0WI&feature=related

I think its a Sample and Hold LFO assigned to modulate the frequency(or maybe its to the filter and its the resonance that is making the random notes?). There is constant random notes in the main riff. I've gotten similar sounds from sample and hold LFO's on my synths. If they did do that riff that way they kind of fluked one of the greatest riffs in dance. They probably recorded ages of random notes and heard that savage riff somewhere in the middle and then sampled it and looped it. Great bunch of lads


Edit: Just double checked there now on my Evolver Synth. Something like the Rez main riff can be got by taking a plain bass sound with no modulation and put some distortion on it, then put a Sample and Hold(may be called Random on your synth) LFO destined to the the Low Pass Filter. Put the resonance up high and put your Low pass Filter low. Keep the LFO frequency or maybe called speed on your synth at mid level. Then just hold down one note on your keyboard and you'll get squelchy Rez sh!t. The same should apply to any other synth with a Sample and Hold(again it maybe called Random on your synth) LFO.

Thanks Valcin, nicely explained. I think I understand it now. I think you're right about Rez using sample and hold, just listening to it now and it sounds like it's modulating the filter. Great song too, brings back memories. I remember seeing Underworld supporting Bjork in the point many years ago and Rez was one of the highlights. Cheers man!

ogy

in max/msp sample and hold is something that takes 2 signals. an audio signal and a control signal. the audio signal is sampled and passed through but when the control signal passes a specified value the audio signals most recent value is repeatedly outputted, newer audio input is ignored until the control signal comes back down passed the set value.