The LX708, LX706, and LX705 let you select the keyboard tone from the panel or from an external MIDI application such as a DAW. To have the keyboard sound the tone specified from a DAW, send Bank Select (CC00, CC32) and Program Change messages on MIDI Channel 4, and set "SMF Play Mode" to "Internal".
To set "SMF Play Mode" to "Internal": hold down the [] button and turn the [
] knob to select "Internal."
For the Bank Select and Program Change values for each tone, see "Tone List" in the LX708/LX706/LX705 MIDI Implementation.