Looper

A looper records a played phrase and repeats it endlessly, so you can keep playing over it. It creates no tonal effect but is a practice, songwriting and performance tool — and one of the most instructive devices there is.

As a practice tool — You loop a chord progression and practice solos, scales or timing over it — with no play-along track, using your own sound. Conversely, you can loop a riff and work on repeating it cleanly. For the feel of timing and interplay the looper is unbeatable, because you play against yourself.

As a songwriting and performance tool — Loop a rhythm, lay a melody on top, build layers — from sketching an idea to a multi-part solo live performance.

What matters — Loop length (how many seconds/minutes), overdub (adding further layers over the existing loop), undo/redo, sometimes rhythm/metronome functions. Simple loopers have one footswitch for everything (record/play/overdub), larger ones several for smoother handling.

Prominent references — The TC Ditto stands for the minimalist one-switch looper, the Boss RC series (Loop Station) for larger units with rhythm and multiple tracks. Reference points, not buying advice.

Honest about the catch — Looping exposes timing errors mercilessly: a loop point hit imprecisely "wobbles", and that is exactly what makes it an honest practice partner. The looper is not an effect you buy to sound better, but a tool you get better with — provided you use it.