Mus. [It. altissimo very high, superl. of alto high.] In the phr. In altissimo: in the second octave above the treble stave, beginning with G.
1819. Pantol., s.v., Altissimo … applied to all notes situated above F in alt.
1838. Penny Cycl., XII. 54/1. The compass … reached five [octaves] from double F below the base to F in altissimo.
1845. E. Holmes, Mozart, 63. I could not … have conceived it possible, to sing to C in altissimo, if my ears had not convinced me of the fact.
