I propose adding a constructor to Interval that just takes an integer number of semitones representing the distance.

Use cases

The Size is, after all, just a human label, from the point of view of physical information there isn't much difference between a "fourth" and an "augmented third", similar to how there is no physical difference between an E# and an F, they are just human labels that allow us to work more easily with these things.
So I can imagine a simple program that just takes some MIDI input and transposes it by a variable number of semitones, and it doesn't really care about the denomination of the new notes.
In such use cases it would be useful to have a "machine friendly" Interval constructor that just takes an integer distance in semitones.

Proposed implementation

Rename:

• fromQualitySemitones -> fromSizeAndQualitySemitones
• fromSemitones -> fromSizeAndSemitones

Add:

• fromSemitones(int)

The size is inferred as the nearest to the given distance.

See the attached draft PR for details.