Hm, Mahler karioke. Interesting thought. Just for you and your 850 (or so) closest friends. The idea is not totally new, though. In the LP era many moons ago, I once saw an LP called "Music Minus One" for a piano concerto (I think it was Beethoven's Emperor concerto) with just the orchestra. You were supposed to play the piano part yourself. Obviously, the series was not a success, since I've never heard or seen anything like it later.
Roffe
PS. I just googled "music minus one" and it still exists. A search for "Mahler" only gives 4 songs (Frühlingsmorgen, Liebst Du im Schönheit, Lob des hohen Verstandes, and Wer hat dies Liedlein erdacht?), no M8.