wasser@viking.DEC (John A. Wasser) (03/27/86)
> I notice that when you change the delay (within a particular range setting) > the existing signal's pitch changes. I can see how this would happen if > it were a shift register type (where the delay is dependent on the sampling > rate and the number of samples in the delay 'line' remains constant. BUT, > if it is a random access type, and the sampled data is fixed in RAM, why > would changing the delay setting temporarily change the pitch??? There are two ways of changing the delay in a digital delay: change the number of samples between recording and playing or change the rate at which samples are being recorded and played (just like a "shift register" type of analog delay). It sounds like your model uses a combination of the two: It uses changes in the number of samples for range changes (probably doubling or halving the number of samples as you change ranges) and changing the clock rate to allow adjustments within a range (which gives you infinite precision). > Also, on a related note, just how does this gadget work: a device that > allows you to change the tempo of a piece of music while keeping the > pitch constant. The same technology: A digital or analog delay. The trick is to remove samples from the delay line faster or slower than you put them in. As you already know :-) this will change the pitch. You use this pitch change to compensate for the change in pitch when a tape or record is played fast or slow. If you want to slow down the tempo, slow down the tape and use the pitch changer to bring the pitch back up. Radio Shack has (or had) a cassette recorder with such a feature. It was intended for listening to lectures quickly (to save time) or slowly (to make it easier to follow). -John A. Wasser Work address: Usenet: {adobe|acorn|allegra|amd|deccra|decvax|dual|flairvax|glacier|idi| ihnp4!imagen|ios|logitec|microsoft|mordor|nsc|purdue|pyramid| qubix|sci|sequent|Shasta|sun|turtlevax|ucbvax}! decwrl!dec-rhea!dec-viking!wasser ARPAnet: WASSER%VIKING.DEC@decwrl.ARPA EASYnet: {VIKING|RAINBO|MOSIAC}::WASSER USPS: LJO2/E4; 30 Porter Rd.; Littleton,MA ; 01460 Phone: (617)486-2505