By Avene
Wed May 16, 2007 2:57 pm
I'm about to start this track on the MPC500 that I'll be creating entirely from a hi hat sample. It probably wouldn't be so difficult on the MPC4000 with it's synth features, but on the 500 with it's very basic features could be difficult. But it's gonna be a fun challenge.
For this track to work I'll need to be looping fragments of my sample to create sustaining notes that I can play, so figured I'd need to work out a simple way to tune them easily without having to rely on a guitar tuner. And I've just worked out a way it could be possible.
Samples are edited in a measurement of samples. I know, it sounds stupid but that's how it is. When you edit a sample and it tells you the length is say 5673. That's 5673 samples. Analog synths use oscillators which are essentially different shaped waveforms such as sawtooth, square, triangle, sine etc. Obviously named after their shape. A square oscillator played at C2 will cycle for the same amount of time as a square oscillator played from the same key, providing both are tuned correctly to the same pitch. Now I figure by taking a fragment of a sample and have it cycle (loop) for that same length, then it should play back at the same C2 pitch on the keyboard as the oscillators. Makes sense, right?
So I had to work out what length of samples the sample fragments should be looped at in order to match different pitches on the keyboard. I decided to stick with the C keys. To determine the length I recorded a sawtooth played from a softsynth at C0, C1, C2, C3, C4, C5, and C6. I then loaded the wavs into Soundforge and adjusted the loop points to match where the sawtooth would cycle from start to end. I'd play each of these looped and would double check the pitch was correct using my guitar tuner. At C0 and C1 I could loop the sample so the pitch was spot on and wrote down the length of the loop (in samples). The higher the notes, the worse it became. I could only really go as high as C3. At this pitch if I added an extra sample to the loop length, it would go out of tune simply because at a higher pitch like that there just aren't enough samples to loop accurately in tune. I got as high as C4 actually, but it was very slightly off. If you're after a C4, C5 or C6 note, I'd suggest using a sample looped at a C2 pitch, and pitching it up 12, 24, 36 or 48 semitones. Of course some samplers won't let you go that high. I'm yet to try it, but I'm sure it will work. I've used samplers before such as Casio's old FZ1 that let you actually draw your own waveforms within a fixed tuned length. Basically the same principle.
Anyway, I hope this makes sense to at least a few of you out there! Or better still that you'll find this info useful. Just thought I'd share my findings.
Below are the measurements I came up with.
C0 note = 1349 samples
C1 note = 674 samples
C2 note = 337 samples
C3 note = 169 samples
C4 note = 84 samples <--- Don't trust this last one, the pitch is slightly off. At 83 or 85 samples it will be completely out of tune.
Oh, I should add, these are all at a sample rate of 44.1khz.
For this track to work I'll need to be looping fragments of my sample to create sustaining notes that I can play, so figured I'd need to work out a simple way to tune them easily without having to rely on a guitar tuner. And I've just worked out a way it could be possible.
Samples are edited in a measurement of samples. I know, it sounds stupid but that's how it is. When you edit a sample and it tells you the length is say 5673. That's 5673 samples. Analog synths use oscillators which are essentially different shaped waveforms such as sawtooth, square, triangle, sine etc. Obviously named after their shape. A square oscillator played at C2 will cycle for the same amount of time as a square oscillator played from the same key, providing both are tuned correctly to the same pitch. Now I figure by taking a fragment of a sample and have it cycle (loop) for that same length, then it should play back at the same C2 pitch on the keyboard as the oscillators. Makes sense, right?
So I had to work out what length of samples the sample fragments should be looped at in order to match different pitches on the keyboard. I decided to stick with the C keys. To determine the length I recorded a sawtooth played from a softsynth at C0, C1, C2, C3, C4, C5, and C6. I then loaded the wavs into Soundforge and adjusted the loop points to match where the sawtooth would cycle from start to end. I'd play each of these looped and would double check the pitch was correct using my guitar tuner. At C0 and C1 I could loop the sample so the pitch was spot on and wrote down the length of the loop (in samples). The higher the notes, the worse it became. I could only really go as high as C3. At this pitch if I added an extra sample to the loop length, it would go out of tune simply because at a higher pitch like that there just aren't enough samples to loop accurately in tune. I got as high as C4 actually, but it was very slightly off. If you're after a C4, C5 or C6 note, I'd suggest using a sample looped at a C2 pitch, and pitching it up 12, 24, 36 or 48 semitones. Of course some samplers won't let you go that high. I'm yet to try it, but I'm sure it will work. I've used samplers before such as Casio's old FZ1 that let you actually draw your own waveforms within a fixed tuned length. Basically the same principle.
Anyway, I hope this makes sense to at least a few of you out there! Or better still that you'll find this info useful. Just thought I'd share my findings.
Below are the measurements I came up with.
C0 note = 1349 samples
C1 note = 674 samples
C2 note = 337 samples
C3 note = 169 samples
C4 note = 84 samples <--- Don't trust this last one, the pitch is slightly off. At 83 or 85 samples it will be completely out of tune.
Oh, I should add, these are all at a sample rate of 44.1khz.