Tutorials and Topics - Peabody Computer Music

Effects achieved with delayed signalsTutorial 27: Processing—Delay linesOne of the most basic yet versatile techniques of audio processing is to delay a signal andmix the delayed version with the original signal. The delay time can range from a fewmilliseconds to several seconds, limited only by the amount of RAM you have available tostore the delayed signal.When the delay time is just a few milliseconds, the original and delayed signals interfereand create a subtle filtering effect but not a discrete echo. When the delay time is about100 ms we hear a “slapback” echo effect in which the delayed copy follows closely behindthe original. With longer delay times, we hear the two signals as discrete events, as if thedelayed version were reflecting off a distant mountain.This tutorial patch delays each channel of a stereo signal independently, and allows you toadjust the delay times and the balance between direct signal and delayed signal.Creating a delay line: tapin~ and tapout~The MSP object tapin~ is a buffer that is continuously updated so that it always stores themost recently received signal. The amount of signal it stores is determined by a typed-inargument. For example, a tapin~ object with a typed-in argument of 1000 stores the mostrecent one second of signal received in its inlet.A 1-second delay buffer tapped 500 and 1000 ms in the pastThe only object to which the outlet of tapin~ should be connected is a tapout~ object. Thisconnection links the tapout~ object to the buffer stored by tapin~. The tapout~ object “tapsinto” the delayed signal at certain points in the past. In the above example, tapout~ getsthe signal from tapin~ that occurred 500 ms ago and sends it out the left outlet; it also getsthe signal delayed by 1000 ms and sends that out its right outlet. It should be obvious thattapout~ can’t get signal delayed beyond the length of time stored in tapin~.220