For their second EP, Muse returned in 1998 to Sawmills Studios and producer Paul Reeve. Muscle Museum originally appeared on 11 January 1999 on Dangerous Records, again in 999 hand-numbered copies. Its six songs, among them 'Muscle Museum', 'Sober', 'Uno' and 'Unintended', catch the band just before the breakthrough: guitar rock with a Spanish-sounding guitar figure and dramatic vocals. Four of them were re-recorded for the debut album Showbiz, and 'Instant Messenger' later surfaced as a B-side under the title 'Pink Ego Box'. The EP entered the NME Indie Singles Chart at number three and brought Muse their first national attention, helped by Steve Lamacq playing tracks from it on BBC Radio 1.

This edition is a 12-inch on translucent teal vinyl, pressed for Record Store Day.