The HAMMOND ORGAN

Digital delay is really where the more interesting digital signal processing effects happen among which are echo, reverberation, chorus, and vibrato to name a few.  Digital delay is accomplished by using a temporary or short term digital memory where the digital information represented by the audio signal gets stored for a while. Retrieving the contents of the memory after a time lapse results in a delay.

Pitch changing can be done in several ways, one of which is to change the sampling rate which also changes the tempo of music. This is similar to speeding up or slowing down either a tape recording or a record turntable. But digital signal processing can take this one step farther by changing the pitch but maintaining the original tempo. and it can also do the opposite effect where it can change the tempo but maintain the original pitch. Digital pitch changing is a very complex process, so being somewhat lazy, I would suggest of you really want to find out about it in detail, that you do a google search on it where you can read some very detailed descriptions of the actual processes that are involved. Also you should google "eventide Harmonizer," which was one of the original digital pitch changing devices and its description is very interesting.