Gah! I've flicked through every page until Elan became a Dashing Swordsman, as well as every occasion I could remember where Elan sung afterwards, and I still can't find it! Did I flick past it by accident?
The closest I've found is this which has 11 notes, and this which has 10 but none of them are Elan's.
Comics I tried after Elan became a Dashing Swordsman include Elan singing while having his blood sucked, rub, rub, rub my father's face in my uselessness and Therkla's death.
The most notes in one comic seems to be on #41 with 14.
That'll rule out some possibilities for whoever tries after me.