I have a suggestion to make ... I think that is very usefull if as an addition to discographies can someone add the exclusive non album tracks that can someone find at "tribute albums", "Various Artist albums" , side projects, featurings etc
For example:
Lonewolf (Fra) (Exclusive non album tracks):
Lonewolf - Victim of States Power (Running Wild cover) (2005 - Rough Diamonds - A Tribute to Running Wild)
Lonewolf - True As Steel (Warlock cover) [2008 - Tribute to Steel A Tribute to Warlock]
Lonewolf - The Torture Never Stops (W.A.S.P. cover) (from 2010 - The Crimson Covers - A Tribute to W.A.S.P.)
Lonewolf - The Test of Time (non album track) (From VA - 2008 - Long Live Metal !!! Acte premier)

That's always been common practice, be they exclusive or not.

See here, for example: http://www.metal-archives.com/bands/Forefather/781