Key signature A minor as each accidental may be notated explicitly as required, or the piece may be modal or atonal. An example is Bartók's Piano Sonata, which has no fixed key and is highly chromatic. If not bound by common practice conventions, microtones can also be notated in a key signature; which microtonal symbols are used depends on the system. The common practice period conventions are so firmly established that some musical notation programs have been unable to show nonstandard key signatures until recently. The use of a one-flat signature developed in the Medieval period, but signatures with more than one
Shape note followed (ascending) by Sol, La, etc. The first note of a minor key is always La, followed by Mi, Fa, etc. The first three notes of any major scale – fa, sol, la – are each a tone apart. The fourth to sixth notes are also a tone apart and are also fa, sol, la. The seventh and eighth notes, being separated by a semitone, are indicated mi-fa. This means that just four shapenotes can adequately reflect the "feeling" of the whole scale. The system illustrated above is a "four-shape" system; six of the notes of the scale are grouped