I have recently bought a Yamaha MX49, and I use it with my MacBook Pro using Cubase or GarageBand. I use it more to play as a midi keyboard. When enabling the record button on the program, the synth plays the sound in the program, however, it also plays the onboard programmed sound. Is there anyway to turn this off so I can only hear the sound from the program. Thanks.
Yes, there is. By turning LOCAL CONTROL = OFF you disconnect the MX keyboard from the MX tone generator, thus setting it up to be a MIDI Controller. All messages travel initially to the MIDI OUT.
This if found among the MIDI setting in UTILITY mode
Press [UTILITY]
Navigate using the cursors to MIDI, and find "LocalCtrl"
Turn it to Off
Remember to set it back On when you disconnect from the computer, otherwise your MX will make no sound in response to key presses. (page 65 in the MX Reference Manual).