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Synonyms for Alto (same or very similar meaning)

WordNet sense 1 (the lowest female singing voice):

WordNet sense 2 (the highest adult male singing voice):

WordNet sense 3 (used of sounds and voices; low in pitch or frequency):
low, low-pitched

WordNet sense 4 (used of sounds and voices; high in pitch or frequency):
high, high-pitched

From the ODE community, based on WordNetadd/edit