Which instrumental track on 'Ride the Lightning' was co-written by Dave Mustaine?

The Ride the Lightning instrumental track co-written by Dave Mustaine is “The Call of Ktulu.” It closes the 1984 album and is credited to Mustaine, James Hetfield, Lars Ulrich, and Cliff Burton.

The track grew from ideas developed during Metallica’s early years, including material associated with Mustaine’s time in the band. Although Mustaine had already been dismissed from Metallica before Ride the Lightning was recorded, his contribution remained part of the song’s official writing history.

“The Call of Ktulu” is an entirely instrumental piece built around ominous guitar figures, shifting sections, and Cliff Burton’s prominent bass work. Its title references H. P. Lovecraft’s fictional entity Cthulhu, though Metallica used the spelling “Ktulu.” Burton’s playing is especially noticeable in the song’s melodic bass passages.

Listeners sometimes choose “Orion,” another famous Metallica instrumental, but that song appears on Master of Puppets, not Ride the Lightning. “To Live Is to Die” is also a later instrumental, released on ...And Justice for All.