Definify.com
Webster 1913 Edition
Tasto
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Tas′to
(täs′tō̍)
, Noun.
[It.]
(Mus.)
A key or thing touched to produce a tone.
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Tasto solo
, single touch; – in old music, a direction denoting that the notes in the bass over or under which it is written should be performed alone, or with no other chords than unisons and octaves.