BOAC
You are using the word ‘song’ when you really mean ‘style’. There is no song on the keyboard called “There’s no Business like Show Business”. What there is, is a suggested style for that song. The only songs on the keyboards other than a few demos are the ones YOU play and record.
Styles are generalized backing tracks for you to play along with, and they should never be too complicated, because -
1. They need to be used for many songs, not just one
2. They are short in length and have to repeat over and over and would sound very artificial if over complicated.
There are a lot of quite elaborate intros attached to styles on these arrangers, and they may sound impressive - they are in fact often designed to impress new players - but frankly they have quite limited use because they might only fit one song. In fact better players seldom use canned intros or only use the very simplest one, or make their own. As you have discovered it can sound a bit silly to have a very elaborate intro followed by pretty basic playing!
As regards OTS, these are someone else’s suggested lead voices for that style. That is pretty arbitrary. OTS is a useful function if you want it, but if you don’t like it, then pick your own voices. You can save these as a new OTS or a registration for that song. This is a musical instrument, so you have to do things for yourself, to suit your own taste, to fit that song, or just to be different.
If you want highly elaborate backing tracks all the way through, rather than generic styles, then you would have to make them or buy them, either highly customized styles or recorded backing tracks. Professionals sometimes do this to achieve a very studio sounding result in live playing, especially if they sing.
But most players use these arrangers to just play along with styles.
Mike