Yamaha Portable Grand DGX-630 Owner's Manual page 119

Problem
The appropriate display does not appear when the
[SONG], [EASY SONG ARRANGER], [STYLE], or
[VOICE] button is pressed.
The wrong notes sound when the keyboard is
played.
The ACMP indicator does not appear when the
[ACMP ON/OFF] button is pressed.
There is no harmony sound.
The "OverCurrent" message is shown in the upper
area of the MAIN display and the USB device
does not respond.
Possible Cause and Solution
Is another display showing? Try pressing the [EXIT] button to return
to the MAIN display, and then pressing one of the mentioned buttons.
Perhaps the performance assistant technology is turned on.
Press the [PERFORMANCE ASSISTANT] button to turn it off.
Is the [STYLE] button lit? Always press the [STYLE] button first when
you are going to use any style-related function.
The harmony effects (01–26) behave differently according to their
type. Types 01–10, 13 function when style playback is on, chords are
played in the accompaniment range of the keyboard, and a melody is
played in the right-hand range. Types 15–26 will function whether
style playback is on or off. For types 23–26 you need to play two
notes at the same time.
Communication with the USB device has been shut down because of
the overcurrent to the USB device. Disconnect the device from the
USB TO DEVICE terminal, then turn on the power of the instrument.
Troubleshooting
DGX-630/YPG-635 Owner's Manual
119