I got Luluna so, I tried that new Golden Melody ability. It's not as good as I thought sadly. It affect all party members, even non GS girls which is very nice but it works only on turn 5 and don't last on turn 6+ which make this less usefull. I admit, it would be broken if it was for turn 5+. But turn 5 is too late to matter.
I rather had an ability affecting only GS girls but for turn 5+.

Congrats phob for your band. I'd like to make the same but I need to keep my FG for Zinnia comeback and for Halloween 30FG gacha.