Historical clue formulations

• Sound of a good car engine — 2025-10-29
• Nothing needs to be said to do it — 2025-09-06
• Keep one's mouth shut, but not stay silent — 2024-09-28
• Fire on all cylinders — 2024-05-09
• Run smoothly, as an engine — 2023-05-22
• What many air conditioners do — 2023-01-20
• Make music on a kazoo, say — 2022-05-09
• Keep one's mouth shut? — 2022-01-16
• Generator's output — 2020-05-23
• Sound from a fan — 2020-04-12
• Bees make it — 2020-01-03
• Background noise — 2019-07-13
• Operate smoothly — 2019-07-10
• Well-tuned engine output — 2019-04-06
• Vocalize on a kazoo — 2018-05-14
• Good engine sound — 2017-12-11
• Good noise from an engine — 2017-03-21
• Run smoothly — 2016-09-22
• Fan noise — 2015-07-28
• Be busy — 2015-06-28
• Beehive sound — 2013-12-30
• Run smoothly — 2013-07-28
• Run nicely — 2012-04-08
• Accompany musically, maybe — 2011-06-16
• What fans do — 2010-10-20
• What you can do if you don't know the words — 2009-12-07
• Symptom for a car mechanic — 2008-09-13
• Make music on a comb — 2007-10-03
• Play a kazoo — 2007-04-24
• Run smoothly — 2006-11-22
• Run smoothly — 2005-10-21
• Be busy — 2003-12-11
• Use kazoos — 2003-11-13
• Run smoothly — 2003-09-02
• Be busy — 2003-04-20
• Proceed without the words — 2000-12-10
• Be busy — 1999-12-16
• Be busy, as a bee — 1998-03-19
• Continuous sound — 1997-03-02
• Continue without the words — 1996-11-10
• Be busily active — 1996-05-05
• Proceed smoothly — 1994-02-10