Stealing bits of Pathfinder....

[Talya]

Spells are a better use of their actions. In PF they can sing and cast in the same round which is more than twice as good.

By the time you sing the 3rd song your party won't even get much mileage out of it in 95% of fights. You're buffing the cleanup efforts. It's almost a waste of time to even bother with it.

It boils down to action economy. More buffs would be nice if they were always active, but they cost an action and there are better things you could do with your actions. On 95% of adventuring days you aren't limited by the number of things you can do you're limited by time so the extra uses beyond that time are 100% useless.

So many ways around all of that...

Melodic Spellcasting.
Harmonizing weapon (preferably on a crystal echoblade).
Song of the White raven.

You're a melee monster, who's singing two songs all day if need be, AND can cast spells without stopping.