Well I know that the graphics must be in 1-bit. But... is it absolutely necessary to make music in 1 bit?

The music does not need to be in 1-bit. We've found that making strictly 1-bit music is often outside of the reach of new developers, and the tools to do so are typically pretty confusing to use. Any developer that does make 1 bit sound will certainly be met with a better score, though. Consider it an extra personal challenge :D