[1] : The Collaborative International Dictionary of English v.0.48

tasto \tas"to\ taums"t-o, n. it. mus.
   a key or thing touched to produce a tone.
   1913 webster

   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.
      1913 webster
see also:
tasto solo 

Tasto >> T Words
Tasto, definition of term: Tasto
tasto_pag1.html

Tasto Solo >> T Words
Tasto Solo, definition of term: Tasto Solo
tasto+solo_pag1.html