Possible Clues:

• Singer's wavering tone
• Violinist's effect
• Pulsating effect in instrumental or vocal tone
• Very briefly, I spoilt child, having got old and wobbly
• Vocalist's effect
• Wavy tonal quality overdone by a lot of "American Idol" hopefuls
• Sextet to include dissonant bar for tremulous effect
• Oscillatory effect
• Singing effect
• Badly-behaved child breaks instrument in half — that's one way to play!