SOLVED - Simple really - er - when you know! Many, many thanks to Kent of PG Support for working it out. Herewith paraphrased quote from Kent so others can see and understand. -
The Chord Builder uses the MIDI Thru channel. When using an MME audio driver (looks like you are), MIDI Thru is routed to the MIDI Output Driver, which you've selected (correctly) as the Microsoft GS Wavetable. From the screenshot you posted in the forums, Band-in-a-Box itself appears to be set up correctly.

However, you're using Windows XP, correct? That version of Windows had a separate volume control for MIDI sounds, and it would get turned down to 0 automatically after playing a MIDI file in Windows Media Player (this was a constant issue when XP was still common). This would be why other users with more recent operating systems weren't able to replicate the problem.

I haven't used Windows XP in a while, but I believe if you hit the Start button, then Control panel, Sounds and Audio devices, Audio, then Volume, you'll find the mixer. Look for a slider marked "MIDI" or "SW Synth", turning it up should solve the problem.
It certainly was that although I have no idea when, if ever I touched that volume slider. It must be that WMP messing it about as per Kents answer. Ace!! One of the joys of the old XP Pro.
Thanks for all those who contributed to this thread.
Ian[b][/b]

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