The Arpeggio Archipelago is a set of Island Cities and towns, all themed around music. They lived in unison, playing many songs and sharing each one with each other.
Until one day, Theodosia River implanted a rule where all Districts must be separated, no longer allowed to mix music as its "anharmonic".
Runaway teens, Bellatrix River (Xe/They) and Beau Eris (He/She) take on the world under the band name Trix and Treble to bring back the joy of mixing music and changing your tune in each of the 6 Districts, while making friends, enemies and music along the way.
See the summary here.