Thayil later contributed guitar tracks to Steve Fisk 's 2001 album 999 Levels of Undo , as well as Dave Grohl 's side-project album Probot , released in 2004 . Thayil later contributed guitar tracks to Steve Fisk 's 2001 album , 999 Levels of Undo , as well as Dave Grohl 's 2004 side-project album , Probot .