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
Key signature only sharp in the G major scale is F sharp, so the key signature associated with the G major key is the one-sharp key signature. However, it is only a notational convenience; a piece with a one-sharp key signature is not necessarily in the key of G major, and likewise, a piece in G major may not always be written with a one-sharp key signature; this is particularly true in pre-Baroque music, when the concept of key had not yet evolved to its present state. In any case, more extensive pieces often change key ("modulate") during contrasting sections, and only