Historical clue formulations

• "Britain's first family of harmony," per Brian Wilson — 2021-12-18
• "How Deep Is Your Love" group, 1977 — 2017-12-09
• "Saturday Night Fever" trio — 2004-12-29
• "Saturday Night Fever" group, with "the" — 2004-12-13
• "Night Fever" group — 2004-01-21
• "Tragedy" pop group, with "the" — 2003-02-01