Hi Byron,
Perhaps your boss is too critical! (sorry)
The frequency-switching arrangement we devised together at http://ez.analog.com/thread/37954 used a slew volume control to gate each frequency bin on and off:
Problem is, this volume control slews at the same rate up and down, forcing a compromise. You would really prefer a fast attack, slow decay to provide the most natural sound. While experimenting with a similar circuit for music, I've found a more refined method as shown below:
With this version, the Running Average Envelope block provides a rapid turn-on response, but ramps down smoothly. You can tweak the attack and decay independently as needed. Perhaps this will meet your requirements.
Best regards,
Bob