For more than two syllables, one could take off final vowel & add -ist: e.g. concertinist ~ and even, sometimes just for 2 syllables, which is what one does, after all, for cello.

But doesn't sound right for all ~ banjist: no, not really. Nor violist. Nor tubist.

Adding a letter, as in lutenist, can work sometimes.

All a matter of what sounds right, as always: that thing called "The genius of the language"....

~Michael~