Possible Clues:

• Tone with which doctor plugs drain
• Quality of sound marginally better initially, having blocked exhaust
• Musical tone color
• The quality of sound coming from spinet I'm breaking
• Occasion overwhelms first baroness meeting Maria in the middle of The Sound of Music?
• Rice gets British capital for Evita — or The Sound of Music
• (A sound's) character
• Doctor probing flag's colour we hear
• Voice quality starts to become resonant eventually?
• Sound wood of sound quality