The PO-20 Arcade is a super fun and different way to make music,

I'd recommend the Arcade for instance if someone wants to compose songs while riding the bus, assuming they like early videogame music

Teenage Engineering leads the industry in creating electronic music instrument layouts, and their genius is shown wonderfully in their Pocket Operater series, especially this Arcade

Using chords numbered 1-16 (each number corresponds to a preset chord, like Dm, Em, Esus, E, F, G, C/G, etc.), you can program a chord progression up to (I believe