Hi rock123456789,
most (commercial) MIDI files are programmed relatively "loud" (relatively high Velocities of the Note events and/or relatively hight Channel Volume values).
I recommend to reduce the SONG Volume (in the Balance display) to a value between 60 and 70. (I always work with a Song Volume of 70.) Then you will have enough "power" for the Keyboard Voices (Right 1/2, Left).
If a Keyboard Voice is already set to 127 (in Balance display), and the Voice is still too low, you can go into
the Voice Set of this Voice and increase the "Volume" parameter there. (Most Voices can be made louder with this "trick".)
You can save this altered Voice as a "User Voice" file (using the "Save" option in the "Voice Set" display). Alternatively you can memorize all your current Keyboard Voice settings to a Registration.
Best regards,
Chris
Don't forget
A midi file takes control over all settings
Best way is edit the midi file
And the best on computer with sequencer software
Use the midi usb cable and install the usb driver
Go to the mixer and editor and make chances
Save the settings in the midi file
When you use the keyboard then you have to make for every midi files user voices
And a fixed volume at start of a midi file are overruled by settings in the midi file
I remove all settings in a midi file and make a remix with the best voices included mega,live,
and voices in expansions packs