Sinister is a song from Doom.
Sinister is played in E2M6: Halls of the Damned and, if Ultimate Doom is installed, on E4M7: And Hell Followed.
Its internal lump name in the IWAD file is "D_E2M6". This track is not included in the shareware version of the game.
Sinister plays during the installation of Windows 32 Doom port called Doom 95. Rather than having the MUS format as all the Doom music tracks belong to, Sinister is an external file with MIDI format located in the same folder of the installation executable. Otherwise, this song plays in the levels of the original DOS release (E2M6: Halls of the Damned and E4M7: And Hell Followed).