1: [Young]
Wings and fins and feathers and one giant tooth: that's a lot of bells and whistles packed into such a little tyke! Okay, while it sports no bells per se, the larval Krillby is basically a whistle. By taking air in and forcing it through channeled ducts in its interior thorax, it produces a sound that is pure and sweet and, yes - clear as a bell.
2: [Adult]
Wings, feathers, and prehensile forelimbs? Yes, the Krillby's morphology is a bewildering hodgepodge, but its song is as sweet and simple as can be. Fleet of foot yet largely flightless, this Monster sports wings for temperature control and dramatic effect, though not necessarily in that order. Because, at first glance, this species looks like it could be tasty, most Krillbies develop their culinary skills and cook hearty meals for the others, to offset any untoward appetites.
3: [Prismatic]
This Krillby returned from the Prism Gate forever changed! Even though the Quad in question already had a diverse assortment of wings and fins and feathers, it has been altered at the molecular level to become a new colorful, chimeral version of itself -- extraordinary!