Owner's Manual
Page 110
...PSR-550. Set the HOST SELECT switch to a computer and take advantage of the wide range of the personal computer and the PSR-550. Connecting to a Personal Computer Connect your computer features a USB interface, we recommend using the Yamaha UX256. The PSR-550 can be connected in the application software to the MIDI... IN terminal of the MIDI interface you are using....
...PSR-550. Set the HOST SELECT switch to a computer and take advantage of the wide range of the personal computer and the PSR-550. Connecting to a Personal Computer Connect your computer features a USB interface, we recommend using the Yamaha UX256. The PSR-550 can be connected in the application software to the MIDI... IN terminal of the MIDI interface you are using....