Hi,

you could try the freeware "PSRUTI", itīs usually written for Yamaha PSR-Keyboards, but (batch-) revoicing is very easy with it wink.
I used it to revoice my Yamaha-Tyros1-files to GM ("GM-revoicing") and then the "midifile Optimizer" ( 150 €... ) to revoice it to Audya.

Youīll find it HERE

For english language scroll down a bit wink
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Greetings from East-Frisia ( Northern-Germany )