What's a loop? It's a sample of sound that's recorded and repeated over and over again, a technique used extensively by hip-hop artists and cutting-edge pop musicians like the Beatles (think of "Revolution 9," among other tracks). The majority of musicians who use looping make music that can be generally defined as "electronic," like hip-hop, techno, drum and bass, etc. But there's a growing movement of acoustic instrument players who use samples and looping to create interesting new soundscapes with the same guitars and cellos and violins that everybody else is using -- and changing the art form in the process.
Scottish rocker KT Tunstall is one of these -- she plays guitar through a custom loop pedal that she's affectionately dubbed "Wee Bastard." There's a great YouTube video of KT explaining how fun & easy looping can be to a lucky young guitar player -- and they proceed to write a song together using loops (and random animal trivia). Witness the flossiness:
The musician who first drew my attention to acoustic looping, though, was multi-instrumentalist Andrew Bird. He plays guitar and violin and mainly loops the latter, which he tends to accompany with some very proficient whistling. (I'd like to nominate Andrew as rock's preeminent whistler.) Here's a delightful song called "Plasticities," which he starts off by laying down layer after layer of violin loops (notice he plays the violin kind of like a guitar here, plucking its strings), and then puts the violin down and picks up an electric guitar. After a rocking chorus or two, he even picks up a mallet and plays the xylophone!
Finally, another acoustic looper has recently come to my attention -- the prodigiously talented "avant cellist" Zoe Keating. She's played gigs all over the world and recently toured as Imogen Heap's opening act, but here's a nice low-key performance of hers -- in the San Fransisco airport.