Loose Blues (released as Unknown Session in Japan) is an album by jazz pianist Bill Evans released on the Milestone label, featuring performances by Evans with Zoot Sims, Jim Hall, Ron Carter, and Philly Joe Jones, recorded in 1962.

This was, in fact, believed to be a lost album since producer Orrin Keepnews could not find the master reels of the session dates, except for a take of "Loose Bloose".

Keepnews, recalling the sessions, stated that "My Bells", which is characterized by difficult tempo changes, took 25 takes to be recorded properly.

The Allmusic review by Scott Yanow states: "Due to some difficulties during the recording process (none of the sidemen were familiar with the often complex numbers), the results were originally shelved and lost for a couple of decades.

This CD reissue shows that the music was actually much better than originally thought..., It is a pity that Evans and Sims (a logical combination) never did record together again.