I'm looking for an object that would accept a signal and a number and transpose the signal by that amount. Ideally, I'd also like to find one that would add a number to the frequency of a signal (to predictably generate beat frequencies when the original signal and the modified one are combined), though I realize that this might be a lot more difficult.
I've looked where I need to look, and poked around at creating them, but haven't succeeded in finding them or getting them to happen. Any clues?