The HSC for music 1 is 80% consisting of 4 electives (any configuration of performance, viva voce or composition I believe) and 20% is a 1 hour aural exam
The HSC for music 2 has one performance, composition, musicology (more music theory oriented) and a 1.5 hour aural exam (the part that surprised me was that you have to sight-sing a melody for one of the exams)
The content for music 2 is much more in-depth, about the different music styles like Baroque as far as I know.
Music 1 is much more performance oriented, since my class chose 4 performances for their electives.