I mean, the stuff you quoted, even bolded,
explicitly talks about things that aren't music: "a master of song, speech, and the magic they contain." Which, sure, it means there's some music in there. But it also means there's some stuff that's explicitly
not music. That would seem to conform to what Jayoungr said, that they're walking back from Bards being 110% musical ALL the time, even when
helping people concentrate or sneak around. That their magic can involve words alone. The music stuff is already baked in (getting three instrument proficiencies and Song of Rest), so everything else can, at least in theory, be covered by the "magic [speech] contain[s.]"