Just in case anyone is interested, I picked up one of the tenders at a local hobby store.
I asked for an in-store demo and was pretty impressed.
The chuffing sound is linked to wheel rotation, and there is an electronic digital whistle and bell sounds that can be activated.
But once I got the unit home I made some additional discoveries. When you press the whistle button, the chuffing stops. Same with the bell. It's one sound effect at a time.
The tender also features automatic and triggered audio crew commands. Wish it could be disabled...
After a few minutes of running, the whistle function seemed to activate itself for brief bursts...
Ended up more disappointed than pleased... But it could be a great accessory depending on your own needs...
Chet