How I think the Mythical Monsters speak/communicate

G'joob has a deep voice and speaks with a major lisp due to its tusks. It sometimes incorporates musical notes into its speech, as is typical for many Monsters. Same for the Rare and Epic.

Strombonin speaks normally. It has a quiet, somewhat deep voice with a slight Japanese accent. Its Strombone "speaks" in trombone noises — being a critter, it's more like an animal's calls than a complex language. Only Strombonin understands what the Strombone is communicating. Same for the Rare and Epic and their respective critter companions.

Yawstrich speaks normally, and sounds like it does in-game. Same for the Rare and Epic.

Anglow produces speech in the same way it makes its synth sounds, resulting in a bizarre voice with strong vibrations, which allow it to be clearly understood when speaking underwater. Same for the Rare and Epic.

Hyehehe speaks normally, and sounds like it does in-game. Same for the Rare. The Epic only speaks through its hand puppet.

Being an arthropod, Buzzinga has no vocal chords, so it communicates with a combination of playing notes, buzzing, and footwork. This is known as the Arthropod Dance-Dialect of Monstrous, and it's also used by other arthropod Monsters such as Humbug and Arackulele. Same for the Rare and Epic.

Cherubble communicates through its dream-projecting powers, and can create both sound and images. I headcanon that the Common mostly uses images, the Rare mostly uses speech sounds, and the Epic mostly uses text.

Cataliszt's speech sounds like when a cat learns to mimic human words. It can also communicate by plucking its cradle, but doesn't do so as often. Same for the Rare.

Bleatnik speaks normally, though with a bleating accent, and sounds like it does in-game. Same for the Rare and Epic.

Cranchee speaks normally, and sounds like it does in-game (except underwater, where it has a very smooth and pleasant voice). Same for the Rare and Epic.

Sporerow speaks in a deep hooting voice, and also uses beak clicks, thumps, and Shroomite pops to communicate. The Shroomites do not speak. Same for the Rare and Epic and their respective critters.

Pinghound can speak, but mostly just barks. It can also use its ping sounds to communicate. Same for the Rare and Epic.

Wheezel has a scratchy voice, and speaks by shouting unsettling words. Its most used word is "NECROSIS." Only Hyehehe, Cherubble, and shLep can understand what it means. Same for the Rare. Due to being created by Yawstrich, the Epic has a less grating voice and screams a more elegant, esoteric set of words, like "FLEDGE" and "SERAPHIM" and "APOTHEOSIS." Yawstrich vaguely understands it, though not as well as Cherubble.

Knurv is silent except for faint warbling and chittering noises. If it needs to, it can speak Monstrous by playing notes with its ocular nerves, but it prefers to speak with its hands using Monstrous Sign Language. Same for the Rare and Epic.

Despite looking like an arthropod, shLep does in fact have vocal chords, but given that its mouth looks like a bunch of worms, its speech sounds like it's talking with a mouth full of worms. It's barely understandable. Much spitting occurs. It can also communicate by rattling, of course, but it's tiring to do so. Same for the Rare. The Epic sounds a tiny bit more buzzy.