Boo, I see you figured out how to get on!
Actually just about every arranger has a screen you can get to quickly to use buttons to adjust the individual style levels.
The Tyros 4, Roland E80, the Audya, and in fact all the Ketrons, have dedicated sliders. The E50 and Yamaha PSRs have a Balance screen you can leave open or get to in one press that allows you to adjust the part volumes and change instruments.
I agree the sliders are the best way.
It's also very easy, after you adjust the volumes, to save to Registration on any of these instruments.
DonM

did I mention that getting rid of the Rompler and implementing 'disk-streaming' like in the Korg Kronos, would be an huge step forward?

compare 256 mb of sounds with 12 gb....

...but it's SO UGLY! And for $500, it better make lunch and drive me to work too. I think it will take a long time for that look to grow on me. I don't like things that stick out ... like the Tyros screen .... it just upsets the lines of the keyboard body. I like sleek and trim.
I will audition the 3x though .... Frankie's got 2 of mine coming in, I think. lol

How do you install the music stand, when you are learning new stuff?

One of the videos say that the stand attaches to the speaker when it's being used.
DonM

You could always use a separate stand for music if needed.