Some laserdiscs have a secondary audio channel containing just the music score of the film; in other words, you're watching a movie on laser, you switch to an alternate audio track, and hear just the music accompanying the visuals.
A small sampling of films available this way are Chinatown (Goldsmith); the Pioneer Itd. letterboxed editions of Obsession (Herrmann) and Islands in the Stream (Goldsmith); the Criterion pressing of Taxi Driver (Herrmann); Paramount's editions of Fear Strikes Out (Bernstein), Desire under the Elms (Bernstein), Carrie (1952, David Raksin) and A Place in the Sun (Waxman); and the Pioneer Itd. editions of Robin and Marian (Barry), Golden Voyage of Sinbad (Rózsa) and Nicholas and Alexandra (Richard Rodney Bennett). Recent releases include 1941 (Williams), E.T. (Williams), The Omen (Goldsmith), Straw Dogs (Jerry Fielding) and Disney's Something Wicked This Way Comes (James Horner).
Before you rush out and buy a laser player, please remember that the music on most of these discs is in mono and it's the film mix—that is to say the volume increases and decreases in accordance with the sound mix of the movie. A scene might start with music dubbed loud and then as soon as there's dialogue the music might be dubbed barely audible. One notable exception is 1941, which features the complete Williams score in stereo and at a consistent volume.
In addition, a number of other laserdiscs featured isolated music-and-effects tracks—music and sound effects, but no dialogue. Some recent releases with this feature are The Missouri Breaks (Williams) and The Satan Bug (Goldsmith).
Beware: many films have been issued more than once on laser. The edition with the isolated music track may not always be the one readily available.