One problem I see with this idea, though a very cool idea indeed, is that the pedal would need to be able to hear what you tap and immediately associate that rhythm with a measure of time in order to know when to repeat that rhythm. For a human brain, this is second nature, and so it's natural that we might think it easy for a processor to do as well. For example, take the "Shave and a haircut" rhythm below:
Everyone knows this rhythm, and would loop it in their on minds like this:
But for a computer or effects processor to hear and repeat a rhythmic pattern, it must A.) know what a measure is, B. know where your taps line up with the measure, and C. know where to end the pattern. Without this understanding, the "Shave and a Haircut" rhythm might think it should be notated like so:
…and relatively speaking, the durations between the notes are the same as the correctly notated rhythm, so you can't fault the processor for the error.
Worse still, since the Timefactor has no concept of "measures" as we think of them at all, it would very likely read your taps as random events within a duration of time.
Tap tempo is actually very simple. When you set a "dotted 8th" for your delay time, the Timefactor doesn't actually know what a dotted eight is. That's an illusion. It just knows something like "duration(x) = 0.75*interval(tapA, tapB)".
In other words, for a "Rhythm Tap" to work, you'd have to program in a whole level of pattern recognition that currently requires advanced computing and artificial intelligence.
But hey, the Eventide guys are very smart, and maybe they could work this out. It looks like a lot of work though.
