The Pleiades, et al

• Largish singing groups
• The seas and the dwarfs, e.g
• Some Dixieland bands
• Deadly sins and hills of Rome, e.g
• Trio-quartet combos
• Snow White's dwarfs and Hawthorne's gables
• Literary gables and others
• Trios plus quartets

Wiktionary Word definitions in Wiktionary
n. (plural of septet English)