N20: The 20-note music box features a diatonic scale, and it does not include semitones (the black keys on a piano). Most pop songs can be transposed to be performed with these 20 notes. It uses a single 20-note comb, producing a crisp, bright sound.

N40: The 40-note scale expands the range and includes semitones (chromatic scale), offering significantly more performance possibilities. It is ideal for songs with larger arrangements or prominent semitones (such as film scores, minor-key songs, jazz, and classical music). The N40 Standard uses two combs (40 notes total), with the same crisp, bright tone as the N20. The N40 Sublime (SLM) features four combs working in harmony. Each note strikes two comb teeth tuned 14 cents apart (80 teeth in total), creating a dense, rich resonance that replicates the luxurious sound of antique music boxes.

For more details on sound samples, materials, and resonance box differences, please refer to this article: Which Muro Box Is Suitable for Me?