I have found that when setting volume levels for the microphone and harmony, sometimes the volume seems to go away completely. You turn it up and it disappears. Has anyone else experienced this effect. What is it. Is it a defect?

I have had exactly the same experience as you with the levels getting all screwed up. I go to the mixer and adjust the harmony level higher and the volume goes completely away. My suspicion is that as we increase the volume of the harmony voice we are telling the effect processor #4 something it doesn't like to see. If you notice, the effect is usually on a noise gate or limiter effect and I think this could have an affect on the levels. I have to spend more time with this. Now, if you want a really good vocal harmonizer, I've just had a ball today installing and playing with the Solton X1 vocal harmonizer. It's the best on of used yet! The sound is stunning, the levels perfect and it does everything I want a harmony box to do.
George Kaye

Uncle Dave - Believe me, the vocal settings are unuseable on an amateur level. The vocalizer is simply a add-on that doesn't work on the 740. It certainly can't be on the same architecture as even the 8000 unless they left a bunch of electronics out. If it isn't false advertisement, it is real close to that.

I've been using the 740 every Thursday, just because it's already there and set up. I set the DSP 4 to 3-band eq. Although this setting is not adjustable like the manual says, I haven't experienced any volume problems.
I think maybe if the DSP is set to compressor or limiter or some such setting, it is kicking in and affecting the mic volume.
While it is certainly not in the league with X1, or PSR8000 or Digitech external units, it sounds o.k. to me. And I'm very critical.
I think the key is in the e.q. The system there has full graphic e.q. plus exciter and good effects processors. It would make a Casio sound good.
Don

About Vocal Harmony seems to go away, try if this help something:
First I consider that the notes added by the Vocal Harmony, are a little robotic.
The Vocal Harmony volume (Mixer and Auto Harmony On/Off buttons) and
digital effects DSP depth, are not volume type but Dry/Wet type, as a Balance.
This is, e.g. Voval Harmony volume: 1 - we only hear the lead voice; 127 - we only hear the effect/ harmony notes added. So, 64 represent singer voice volume and
Vocal Harmony notes with the same volume. Less than 64 the singer voice is louder
than Harmony and more than 64 the Harmony is louder than the singer voice. For me
30 is a correct value for consider this feature of some use.

The block diagrams of PSR 8000 shows that, before the Vocal Harmony block there are two HP (high pass) filters to correct the mic signal. Te PSR 9000 has a 3 band parametric equalizer more a noise gate block and also a compressor to correct the mic signal before the Vocal Harmony block. The PSR 740 has no of this addicional blocks before the Vocal Harmony block; the mic attack directly the Vocal Harmony. Surely here it is the problem. So, if we use an external mix console with 3 band EQ, gate noise and compresser to correct the mic signal and after we inject this corrected signal to 740, I guess that Vocal Harmony at PSR 740 will work perfectly.
Regards
Carlos Rodrigues