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Synonyms for Treble (same or very similar meaning)

WordNet sense 1 (the pitch range of the highest female voice):

WordNet sense 2 (three times as great or many):
threefold, triple, three-fold

WordNet sense 3 (having three units or components or elements):
ternary, triplex

WordNet sense 4 (having more than one decidedly dissimilar aspects or qualities):
double, dual, twofold, two-fold

WordNet sense 5 (having or involving or consisting of more than one part or entity or individual):

WordNet sense 6 (used of sounds and voices; high in pitch or frequency):
high, high-pitched

From the ODE community, based on WordNetadd/edit