First off some Kvaksulu instruments -
Dukí, Ettud - reed or wooden flutes, higher pitched, shorter in length.
Dásnyl - a more complex and longer woodwind, lower pitched, more clarinet/shawm sounding sort. Made from a special kind of wood with different properties. Its length might be problematic for the player so they need to rest the instrument on some kind of support.
Nuarát - a long, powerful bassoon-like instrument, used to play the lowest voice. Made too from the elf hack wood. Since it's vertical it isn't so hard for a frog to handle, the player rests it against one of their thighs with both of their hands grasping it too, able to reach the holes.
Dárpyhrr - any kind of drum. In bands, tuned timpani-like kettle drums would be used to participate in harmony of the compositions.
Other instruments would be string lutes/cimbaloms, later some kind of bowed instruments too, though I have to think about handling of those. With advent of more advanced machinations Quarlvákaea monasteries would have carillons and later even organs. Both of these I've been already thinking through, the only differences from our designs would be the position/distances of the seat, manuals and pedals to better suit the position and reach of frog limbs.
Completely unrelated, a Friák (punisher), member of the monastery responsible for beating and whipping convicts, among other things.