Historical clue formulations

• Sings like Mary Poppins — 2020-05-02
• Quavering sounds — 2018-12-30
• Vocal quavers — 2017-03-12
• Soprano sounds — 2015-06-01
• Voice lesson subjects — 2014-03-22
• High-pitched warbling sounds — 2006-10-05
• Woodwind embellishments — 2002-07-28