On the SX900 use one of the MIDI templates 'All Parts' or 'KBD & Style'. If this latency cannot be set shorter, you would have to use an additional, external USB audio interface as the audio output on the Mac. Note: If there is an audible delay when using virtual synths as a sound generator on the Mac via the headphone output, this is probably due to a relatively high latency of the internal sound card. The volume control for the AUX IN of the SX900 can be found in the Mixer display (Panel tab, page 2). On the Mac, you should turn up the volume relatively high in this case. If you want to hear the sound generated on the Mac through the SX900 speakers, you have to connect the headphone output of the Mac to the AUX input of the SX900. You can always find the latest USB-MIDI driver by searching for 'usb-midi' in the 'Keyboard Instruments' category on the Yamaha Support Site:

> USB-MIDI Driver V1.0.7 for Mac OS 8.6 - 9.2 > USB-MIDI Driver V1.3.1 for Mac OS X 10.4.11 > USB-MIDI Driver V1.5.0 for Mac macOS 11 (Intel/Apple silicon with Rosetta 2) There are 4 different Versions at the moment (for the different macOS versions): The SONG parts are controlled via port 1 on the SX900 (Receive) by default.) Most of the time you only need MIDI port 1 (as a MIDI input device or MIDI output device on the Mac). (Normally you don't need MIDI Port 2 unless you want to control the keyboard parts (Right / Left) or the Style parts directly from the Mac. If you have problems with the USB-MIDI connection or the second MIDI Receive Port (USB2) of the SX900 is not available as MIDI Output device on the Mac, you can install the Yamaha USB-MIDI Driver. That is why there is no USB-MIDI driver for MAC listed on the SX900 download page:

The Mac should automatically recognize the SX900 as a USB-MIDI device. This is because all newer Yamaha arranger keyboard models are USB-MIDI 'Class Compliant'. In many cases you don't need to install a Yamaha USB-MIDI Driver on a MAC.

Yamaha usb midi driver mac