It's actually quite an incredible hidden feature (probably a mistake by Universal; it was announced but not listed or properly presented on the DVD).I doubt it was a mistake but if so then they did it three times in the same year as Universal's Apollo 13 & in a slightly different form The Thing also feature this.
Of topic.....a few in my collection I just thought about: Goodtimes older release of Halloween II has a very simular "score over menu" feature, The Matrix, Blade & Pee Wee's Big Adventure all feature an isolated score with composer commentary (Pee Wee being in 5.0), Criterion's release's of Spartacus & Straw Dogs have some nice isolated tracks (Spartacus being alternate tracks & Dogs being a music and effects track), Superman has not only an isolated score in 5.0 but has many alternate tracks in 5.0.
And now that I think about it Ennio Morricone's score for Dario Argento's The Bird With The Crystal Plumage is also available on the older DVD release, it is listenable in it's entirety on a separate menu.