Do you mean MIDI's converted to to Yamaha format ?

Generic SMF files can be read by virtually anything, and transferred by a pc. SD Explorer doesn't handle MIDI unless they have been converted to Technics format.
_________________________
pa4X 76 ,SX900, Audya 76,Yamaha S970 , vArranger, Hammond SK1, Ketron SD40, Centerpoint Space Station, Bose compact