RX300 musical tone on light throttle

[CapeCodder]

2000 RX300, 167,000 happy miles. Car recently developed an almost musical tone inside the car when cruising at light throttle, sounds like air flowing over an open tube.

If you give more or less throttle, sound goes away instantly then returns as you resume a steady throttle, occurs throughout the speed range.

Dealer technician diagnosed worn rotors and replaced front brakes, didn't seem to acknowledge the issue was "go" related, not "stop". 

Any suggestions or advice appreciated.