I discovered the drawback of using the keyboard's onboard sound system as a monitor many years ago while playing a large senior center in Bel Air, Maryland. I was using the Bose L1 PAS system at the time, fired up the keyboard, activated my setup registration, then tinkled a few piano notes which sounded fine. The venue held about 300 ppl and there were about 250 in attendance. The crowd noise was somewhat loud and the acoustics were just awful, almost like playing in a gymnasium, hard tile walls, hardwood floors, lots of high, glass windows. This was one of the few times I did not fire up a midi file and do a walk around sound check.

The very first song I performed was Swinging Doors A Jukebox And A Bar Stool. This was a died in the wool country music audience and this song always went over well with them in the past. After the second song, with absolutely no audience response, a lady in the front row came up to me and asked if I could turn up the volume. So I cranked up the main on the keyboard, and she indicated that she still could not hear me. Then I looked down at the Bose L1 PAS, which is a real powerhouse of a PA system and noticed the power indicator light was not on - I had forgot to plug in the power cord. I could hear myself just fine, but the audience, obviously, could not. That never happened again, and I immediately inserted the dead head plug into the headphone jack on the keyboard and the audience came alive for the next two hours.

I'm not sure if anyone else made the same, stupid mistake I did that day, but I seriously doubt that I'm the Lone Ranger in this instance.

Like I stated earlier, I want to hear exactly what my audiences hear. If I don't like what I'm hearing, I'm sure they won't like it as well. As for the keyboard contributing to the overall sound quality with the onboard speakers, I seriously doubt that is the case. Granted, it contributes to what the player hears, but beyond that, I don't think the audiences hear anything other than what is emitted from the PA system at distances greater than 10 to 15 feet, even if the keyboard's volume was cranked up to max.

JMO,

Gary