Thank you!
I think it's hardly possible to get the orchestral sounds as clear via speakers as they are via headphones - and much less if they are additionally recorded via air from the speakers. Additionally, I had to place my Olympus recorder at the side of the speakers, not in front of them, which adds to the indirect sound.

From the angle of the audience, a higher volume of my sounds would have buried the vocals too much, some already said it was a bit too loud at times.

Another factor is that, as I played everything completely live, I was forced to layer a lot, all woodwinds and later woodwings + strings sound simultaneously, whereas a real orchestra would have different solo voices for clarinet, oboe, flute etc. The only way to partially improve this would be having an "ensemble voice" feature available like in Tyros 5 so that at least the woodwinds would be split into separate solo voices - but I'm not sure it would really work out, especially when I also play the piano part simultaneously, use the sustain pedal, play very dense chords with many keys (typical for operetta) and therefore having a lot of keys sound at the same time.