Hi again Lorenzo (and all you groovy loopers all over the globe, and especially the physical contingent representing at the 10th anniversary festival) -
I would seriously consider the DD-20 for your music, perhaps even two.
I will hereafter use the term "virtual sync" to describe the DD-20 being set to a specific delay length equal to, or in a whole-number ratio to, another unit without any MIDI or other clock information being sent/received between the two units. Two DD-20s will stay in virtual sync with each other for at least a half-hour. I've not yet let mine run more than that, but someday maybe I'll put on a rhythmic loop and see how long they stay sync'd before an audible mismatch creeps in.
One of the very practicaal benefits of the DD-20 is its numerical readout for delay length: up to 9999 milliseconds (9.999 seconds), then hundredths of a second (centaseconds?) from 10.00 up to 23.00. I used my DD-20s in virtual sync with the click of my Korg D1600 recording workstation and with my Bodd GT-3 multi-fx pedal to record the excerpt of "The Long Dance" that is on the Looper's Delight Compilation Vol. 3 CD. Neither the DD-20s, the GT-3, nor the Korg required any tweaking of their time parameters to remain in sync for the entire recording process. I often use my DD-20s with a drum machine these days (a Zoom RT223) and while this machine *does* require a slight tweak to get in sync, I can find its "sweet spot" pretty quick and my two DD-20s, my GT-3 and the RT223 will groove away for fifteen minutes or more in virtual sync. I suspect the mismatch between the DD-20s and the Zoom are due to different clock pulses; the Zoom runs about 1% faster than the DD-20s. I'm looking forward to getting a Boss DR-880 in the near future, and I'll bet the entire Boss family will run in exact virtual sync.
You described your music this way:
I let electronic rythmic parts run on the background, and add layers of guitar loops: very simple and generally brief arpeggios, or chords, on which I add solos (sometimes with my ebow), or just very spacey soundscapes (lots of reverbs etc). That is why I need perfect timing control over my loops: they need to be perfectly synchronized with the drum track I run in the background. I guess you could say what I do is somewhere in between Lali Puna/the late Radiohead, Labradford, with a kind of ambient touch to it.
With one or two DD-20s (and/or a drum machine or two, as I just described), you can create a background rhythmic pattern, add as many layers of live-in-real-time guitar textures as you wish, set one or more of your DD-20s to "infinite feedback" to capture your loop, then press the On/Off stomp switch on the left. This turns the *recording* of material off, but allows the loop/delay to *play back* at whatever feedback level it is set at. And if it's set a "infinite feedback," the loop will loop endlessly with no degeneration, no fade, and you can solo to your heart's content. Let's say in the midst of your soloing you play a melody, chord or texture you'd like to add to your loop. Just hit the On/Off switch again (turning the pedal's "record" function on), play your new material, and hit the On/Off switch when you're done. Your new melody/chord/texture is added, and you can continue to solo atop the loop.
For my taste, a delay-based looper like the DD-20 is superior to a "true" looper like the Boss RC-20 because, in addition to being able to end a loop suddenly, the DD-20 can fade out over as long or short a period as you like by adjusting the feedbck level. Currently I'm playing around with groove-based textures that either drift (i.e. the groove slowly dissipates) or leap(i.e. the groove suddenly disappears) into non-rhythmic oceanic soundscape-land.
Hope this helps y'all,
Clouds and clowns!
You don't have to come down!"
- Sly and the Family Stone