Something simple enough to implement but that would set a delay apart from most of what's available now :
- effect loop in the delay's feedback path, so that people could make each repeat go through any effect or combination of effects they want.
Something else, inspired by what I guess is either some hardware restriction or more likely lazy code in the Boss DD20 (but the result is awesome) :
Code the thing so that you're always using a big-ass data buffer in which you record the audio. Use only part of it depending on the delay time setting. Now, the important part : do not delete/reset it when changing delay time. Just keep the data there even if it's not used.
This just by itself is not necessarily awesome, you need to seamlessly access different parts of the delay buffer to make it wonderful. A couple of obvious ways :
- have a series of preset time divisions and enable switching between severaĺof them with a button or footswitch. That's what the DD20 can do. You can easily end up with previous bits of recorded data superposed with new stuff, stuttering sounds, etc.
- more interesting : have an offset parameter that determines the current reading/recording starting point in your data buffer (instead of 0 by default). Then have this parameter accessible through a pot/CV input/internal modulation.
Seriously, that second thing would make an awesome pedal and I'm surprised nobody's done anything like that yet. If you're interested in this idea I can make you a small demo recording of what the DD20 can do when properly abused once I'm back from my holidays...