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Conference hydra::amiga_v1

Title:AMIGA NOTES
Notice:Join us in the *NEW* conference - HYDRA::AMIGA_V2
Moderator:HYDRA::MOORE
Created:Sat Apr 26 1986
Last Modified:Wed Feb 05 1992
Last Successful Update:Fri Jun 06 1997
Number of topics:5378
Total number of notes:38326

4770.0. "Sampling Techniques" by XSTACY::PATTISON (A rolling stone gets the worm) Mon May 27 1991 11:51

  Suppose I sample a couple of bars of music from my CD player. I want to
  use this sample as a loop. So that when I play a particular note, (C-2, say)
  the sample loops such that the beat is exactly 120 bpm (beats per minute).

  Assume also, that the bpm of the original sample is NOT exactly 120 bpm.
  Its slightly off. For example 119.293 (assume I can calculate this accurately)

  So ... can this be done? what sample rate should I choose? I'm using 
  Technosound sampler software and MED V3.0, although I also have AudiomasterII
  and a couple of others.

  Dave
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4770.1Technologically impossible unless it can be doneDFN8LY::JANZENA Refugee From Performance ArtMon May 27 1991 14:5716
	Does your software have a pitch-change "harmonize" function?
	Otherwise you're stuck.	
	You could change the tempo by manipulating the record sample
	rate, but the pitch will go out of tune by the same ratio.
	You must have a pitch change function.
	To raise a pitch, a pitch change function repeats a waveform
	for the same length of time it persisted, and to lower a pitch
	it edits out little pieces of the waveform so that the resulting
	length is the same but the pitch is lower.  This can't be 
	accomplished with just changing sample rates or "resampling".
	(e.g. Perfect Sound's resampling).
	However, it just occured to me that I might be able to
	write a program that did this on a raw sample (spare me IFF
	parsing).
	Tom
4770.2Doesn't need to be that cleverXSTACY::PATTISONA rolling stone gets the wormTue May 28 1991 07:0120
   Re: -1
	>>Does your software have a pitch-change "harmonize" function?
	>>Otherwise you're stuck.	

   I understand, but .....

   Suppose I don't care about the pitch-change, I only care about the timing.
   (The samples only contain percussion sounds, for instance)

   Say I use sample rate S. (Which corresponds to the C-2 period). I want my l
   loop to last 1 second exactly. Using rate S the loop lasts 0.97 seconds.    
   
   I tried "resampling" using AudiomasterII but the results were confusing,
   it cut my sample resolution in half.

   So if I start again with sample rate (S/0.97), should I expect to get a 
   1 second sample on a C-2? Or maybe its not that simple..

   Dave