Aim for at least one octave (C4 to C5) – you can pitch-shift later.
: A free instrument from Fracture Sounds that runs in the free Kontakt Player, offering a "mysterious metallic" sound with atmosphere layers. How to Use Them in Your DAW Synth Music Box (GM Music Box Remake) - Musical Artifacts
If you are composing with a music box soundfont, treating the raw MIDI sound with the right effects will give it life and depth:
If you want to compose your own piece, you can find high-quality music box sounds through these sources:
: Often recommended for its high-fidelity sampling of real mechanical boxes. Olympia Soundfont
Furthermore, the music box is rarely in perfect tune. In a world of Auto-Tuned vocals and grid-snapped drums, the of a real music box sample—which a good soundfont preserves—adds a layer of "human warmth" that modern synthesizers struggle to replicate.
Whispers in the Gears: The Ultimate Guide to the Music Box Soundfont