just use different counters to trigger a line~ to create a different envelopes for different oscilators, or even buffers. another thing which you may effectively need to do is to, within certain regard, to adjust the length of the counters. but that shouldn't be difficult to be made. in ableton live and m4l, there are already a bunch of devices with such an approach. in pd, you may need this, and you may need a few further things,but the basic foundations are those. please note that in the case of the buffers, the only thing you may need is a message triggered by the counter. what about using the zl object combined with a uzi, to generate different list streams, in order to generate complex idm patterns

you need four buffers and you need to record audio into it. that's not tricky. the tricky thing here would be overdubbing the same buffer, which may imply some form of summing of your output audio with your input audio, for each of the buffers. even though i would like to point you to a couple things in here: one would be, and is effecively to use a tape delay with 8 and 40 seconds. the other is using a granular delay line. and finally to use granular synthesis with less voices, very large buffers, very large grains, and so.
cheers