Coincidentally, I just ran into the same problem lowering the pitch of an MP3 on my pc for the same reason. I had a program called MP3 Key Shifter that I used for years, but lost. I downloaded Audacity, which is free, and found it to be even better. Even I found it simple to use, and that's saying something.
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pa4X 76 ,SX900, Audya 76,Yamaha S970 , vArranger, Hammond SK1, Ketron SD40, Centerpoint Space Station, Bose compact