Can confirm, still present in new snapshot - although as far as I am aware no bugs were fixed, only twitch integration added.
Bug confirmed on 1.7.1 pre on Mac OSX Mountain Lion. Seems to only happen to me with two particular tracks (I don't know the names sorry!): The one that sounds like it is being played on a glockenspiel and the one played on a piano.
The orignal two pieces of music that were overlapping no longer do so, however the new sounds are quite remixy - I have heard what I thought was two songs playing together but a quick check on the spotify album showed me this was infact what the song sounded like. This is on the 1.7.3 prerelease snapshot.