In music, the register of notes above altissimo, representing the highest range a musical instrument or voice can produce.
From Italian 'altissimo' (highest) preceded by 'alt-' meaning 'another octave higher,' creating a superlative of a superlative—the highest of the high.
Professional opera singers can hit altissimo notes that sound almost inhuman, but altaltissimo is so extreme that only the best singers or the highest wind instruments can reliably produce these notes without sounding like they're breaking.
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