radio massacre international:
we usually use our loopers over a bed of analogue sequencing, though often the loop will be there without the sequencer lines, either before they come in or after they're gone, or even during an "atmosopheric" interlude between two bouts of sequencer workout.
it occurs to us sometimes that this is a bit formulaic, but then we think "well, what's wrong with that? other types of music use formula constructions too...."
the contents of the loop (& whether or not it's strictly synchronised with the sequencer parts) will vary from piece to piece. the sequencer parts are generally one or two bars of 1/8, 1/16 or 1/32 note patterns played by a variety of analogue synth voices or other percussive/melodic sounds (mbira, marimba, electric piano, white & tuned noise & so forth).
the sequencers are hardware devices- doepfer, notron, sequentix, arp &c.
so the loops are sometimes keyboard parts, electronic noises, bass guitar, noises from microphones (the other keys player is also a drummer, & has taken to using a kit of "toys" adjacent to or instead of his regular kit, which he plays through a mic into the EH16s reissue, not synchronised to anything).
our guitarist uses a jamman for synchronised loops & echo, & a DL4 for non-sync echoes, though he is getting better at tap-tempo.... :-)
as regards the actual hardware- the live rig at the moment contains a repeater (often with a stereo "pad" or loop already in it for a particular number in the set), an echo-pro, the aforementioned jamman & regular DL4, & the EH16s reissue. the master clock for the whole shebang is an electribe es-1, with a nice big tap-tempo button for rapid changes. only the jamman doesn't handle this (tempo change) properly.
at other times, we have also used a second jamman, a DOD dimension 12, a vortex, a modified boss rps-10 (extended "freeze" duration at expense of fidelity), another DL4, powertran MCS-1, bel BD80, two revoxes, two uher portables.....
despite the variety of looping tools at our disposal, the basic approach is to allow or to force degradation of whatever is looping before it becomes tiresome. I know that's a bit vague..... what we'll either do is add layers to the loop until the first pass is inaudible, or else distort the loop contents by running them through effects & rerecording them, or punching holes in them (by dropping in & out of record with o/dub turned down) to create a rhythmic effect.