The tiny Olympus WS-311M captures surprisingly  useful stereo sound, especially with external mics such as these Sound Professionals SP-TFB-2 binaurals ($79, soundprofessionals.com).

Electronic musicians are blessed with dozens of choices in portable, high-resolution digital recorders. But for years, I've carried a lower-quality recorder everywhere I go. The Olympus WS Series digital voice recorders capture 16-bit, 44.1kHz stereo, start around just $50 and slip easily into a pocket. An integrated USB plug offers fast computer transfer. Sony offers stereo models, too.

The sound isn't great: There's automatic gain control, pronounced handling noise, midrangy mics and hiss. (External mics help a lot.) The Olympus recorders save files in compressed WMA format, which requires the free Flip4Mac QuickTime extension to edit on a Mac. But convenience trumps quality here. Like a cellphone camera, a pocket voice recorder is always with you, ready to capture the wonders of the world. And when layered subtly under music, the thin sound blends well, adding an evocative texture.
— David Battino, Batmosphere.com