There was x11amp, which got renamed to XMMS, which was later forked into Beep Media Player, which was later forked into Audacious.

IIRC, the last time I used Audacious, the default interface was a loosely-inspired-by-itunes kinda UI, but tweaking the right knobs in the configuration screens could get it to a Winamp-like UI (or at least XMMS-like)

https://en.wikipedia.org/wiki/Audacious_(software) confirms a lot of my recollection.