I think the former.
http://theconcerthall.yuku.com/topic...e#.T3pFBNU2W00
"Must be held in primary hand for instrument effect (confirmed with Sonorous Clouding)."
I'm looking to find the crying that the SSS wasn't primary equippable at all but I'm not finding it.
EDIT: To add, the current SSS on P99 does not have the correct 100hp/0mana at the moment last I heard from Fauss. IIRC the other stat adjustments were correct.