When I use the Vellicosa's dot line it says scales damage from 8 (L8) to 100 (L60). But the base damage while singing is at 85, with a singing skill of 305.
So something seems slightly off. Singing and Level should put the song at the stated caps right?
I have a relatively low brass skill about 100. So it seems it is either using the Brass skill value, even if you are singing to determine the scaling or something is definitely weird here.
I would expect that if I sing the song at Level 60 I would see 100 damage onto the mob per the description, and then if I use a Brass Instrument (in this case), the song effect increases.