Cassie Walkman (And oc that came into being.... today, basically) is a robot with a love of sound and sound synthesis. They've modded themselves to have a complex synth engine embedded directly into their head, which they use to speak, and have exposed dozens of parameters via the network of patch cables that make up their 'hair'.
Cassie was originally a robot sold by a company but... any knowledge of that has been lost to time. Cassie has 'Ship of Theseus'd themself multiple times and contains few, if any, of their original parts.
They have a chaotic, free spirited nature, largely doing whatever the hell they want - which involves a lot of sampling and messing with their voice. It's rare to hear them sound the same more than one day in a row.