Yamaha CP5 usb to host playback issues.

Hi, I play on a Yamaha CP5. I just recently started experimenting with usb to host and the midi options with that. I plugged my computer into the usb cord and it recognized (after I downloaded the yamaha CP5 driver software) that there was a MIDI input. I did this with several other keyboards and the playback worked, but with this keyboard I could not get any sound to go through to the mac. Any suggestions???