How to Transpose (change Key) with MIDI on WK-6500?

[lilsoulfish-hk]

I loaded a MIDI to an SD card for the first time. It's magic.
the song is in the key of D
my band would like to play the song in C instead

So I thought I could use the transpose function to make it -2

However, all it does is change it to an octave higher or lower.

I tried looking for a solution for an hour in the manual and Google, but no luck.
Hopefully, the community here can help a rookie like me. Thanks in advance!

 

[Mclandy]

You may need to change the key of the midi file using some MIDI/DAW software before loading it on the card.  Note, per the User Manual on page E-108, the Transpose setting will automatically change to 00 (no key shift) when you start playback of a music file on a Memory card.