Yo

The bright half of a pair

Japanese theory sorts pentatonic material into in and yo. The in scales contain half steps and read as sombre; the yo scales have none and read as open. Yo is the type specimen of the second group, and hearing it beside in-sen is the clearest demonstration of what that division means.

This is a different axis from the Western one. Western naming sorts scales by their third and sixth, so it has no single word for what in and yo distinguish — the presence or absence of half steps — and that is exactly the feature these two traditions organise around.

The same notes as Ritusen

Yo has the same intervals as the blues major pentatonic, which is also listed under the name Ritusen, after ritsu — one of the two principal scale categories in Japanese court music. The duplication in this catalogue is real, not an error: several naming systems converged on one set of five notes.

What differs is everything around the notes. Ritsu names a category within gagaku theory; yo names the bright type in opposition to in; the blues major label comes from Western pentatonic practice. The intervals are identical and the repertoire, ornament and phrasing attached to each are not.

How it is used

In Japanese folk song it is the ordinary material, which is worth stating plainly: yo is not exotic in its own tradition, it is the common scale. Warabe uta and much min'yō sit in it, and it carries none of the signalling weight that hirajoshi has acquired in Western scoring.

Outside the tradition it behaves as any anhemitonic pentatonic does — safe over sus and quartal harmony, useful when a third would over-determine the sound.

Confusions and neighbours

The common mistake is expecting it to sound Japanese in the way hirajoshi does. It does not, because the marker Western ears respond to is the half step, and yo has none. A melody in yo reads as folk-like in general rather than as belonging anywhere in particular.

It is a rotation of the major pentatonic and identical to the blues major. Within the Japanese group its counterpart is in-sen, and playing the two from the same root is the fastest way to hear what in and yo mean.

Frequently asked questions