I don't own one of these keyboards, but I poked around Yamaha's website, and it looks like you simply can't do what you want to do. It looks like Yamaha writes to the USB storage device in a proprietary format which can only be read with their MusicSoft utility, which is only written for WinTel PCs. Maybe you could run a PC emulator on your Mac?

Actually, I just got to thinking. If you simply want to back up the contents of the USB storage device onto the computer, then you should be able to plug it directly into the Mac and use Disk Utility to create an image of the USB device.

vttom, post: 353976 wrote: Actually, I just got to thinking. If you simply want to back up the contents of the USB storage device onto the computer, then you should be able to plug it directly into the Mac and use Disk Utility to create an image of the USB device.

Thanks. I'll probably see if I can find a PC emulator.

Some good news: I tried a different USB storage device and now it works! I formatted a USB storage disk in the keyboard, saved a couple of songs to it and moved it to the Macintosh. There is a folder called USER FILES and inside that are the .MID files.

So apparently you CAN use a USB storage device with a Yamaha P155 and a Mac.

This sort of related but the other way round.
I prepare files on the Mac and load them onto USB, numbered in a specific order.
However, on the P155 the order is changed, so I don't know what where.
Haven't had this problem with other Yamaha pianos, eg Clavinova.
Can anyone help?