@ (not that) Adam -- It says '... choose a target who can hear you and roll +CHA. On a 10+ the target flails in confusion, dealing its damage to a creature of your choosing.' So I read that as it just deals its damage, no HnS roll required.
@ Skinnyghost -- 'On a 7-9 it deals its damage, but then takes +1d4 damage ongoing as the music invigorates it.' I don't read this as implying that it continues being confused after the first instance of confusion, but either way the 7-9 is really strong:
If the confusion persists, then 7-9 is strong because the party can stand back, Defending the Bard, and let the enemy monsters get ripped apart by their buddy.
If the confusion doesn't persist (merely invigoration, as the text reads), then 7-9 is preferred because you can cast it on an ally.