In many ways it pioneered some film technics now common. The use of music as part of the scenes (diegetic).
The diegetic aspect is something I hadn't even considered. I'm trying to think of subsequent films that employ it throughout most of the scenes (plenty of examples of isolated use).
"Dazed and Confused," which I cited earlier as being influenced by AG, music is almost exclusively an accompaniment to action — although sometimes SEEMS like the characters can hear it, too (but that' viewer interpretation, and mine specifically).