I can easily think of one scenario where it could be midly beneficial.
You're doing content with some friends, you just apply 10+ mins songs to the pt thanks to Nitro.
Someone suddenly dies.
Normally at that point you'd be forced to recast 2 songs + 2 fakes + overwrite the 2 fakes with real songs (at best) to give them ~6 mins duration.
Meaning that BEFORE the 10+ mins songs expire on the other pt members, you would be forced to pianissimo songs again on that guy so that his songs won't expire and so that he will mantain 4 songs and be ready for the next turn of NiTro.
With this instrument you could do the same but without the "recasting once more" aspect.
All of this at the cost of losing +1 potency, which I'd say it's sorta reasonable.
Kinda niche if you ask me but it is what it is.
Other uses... I dunno.
Supposing it stacks with Soul Voice potency (it should, shouldn't it?) then to give 15-18 mins duration SV at the cost of
+1 +2 potency.
Last but not least for all situations where you want 10+ duration on songs but you cannot use NiTro (or don't want to use it).
All at the small cost of +1 potency.
I dunno, it sounds extremely niche, but I guess it can have its uses.