With regard to creating new styles on the KN7000, I've been doing this for quite some time now - thanks to the great editing facilities provided for us in the Composer.
I found that although most of the built-in styles are very good, they are mostly designed to be 'General' rather than 'Specific' for a particular song or tune. That comment in no way, is intended to criticise the 'authors' of the built-in styles.
When I construct a sequence - particularly some of the more modern Songs/Tunes, I try to get as close to the 'feel' of the original arrangement, as the KN7000 will allow. I find that one of the most important components of the arrangement, is the Bass Line and it is often not possible to achieve the desired progression, when the notes played in the Bass Part, are just left the Auto Accompaniment 'Intelligence'.

There are two ways to overcome this problem :
1. In a Sequence, write the Bass line as a completely separate track within the sequence and turn off the Bass part in the Auto Accompaniment.
2. Use a facility within the Composer, to force the Composer style to play the desired Bass notes, which you would enter into the Bass Part.
Although the overall Sequence will sound the same, no matter which option is chosen, I prefer to use option 2, since this option allows the Style to be used, with the 'correct' Bass line, without having to use the Sequencer, particularly if someone else wishes to use my Composer Style and play 'live'.

Most of the Songs/Tunes which I have recently sequenced, have used Composer Styles, which I created from scratch, by either listening to the original recordings and determining what is going on in the 'backing' to the melody, or, having in mind, the kind of 'backing' which I feel is suited to the melody. You can listen to them on the WMA page of my website http://www.willumspages.co.uk/page9.html - songs from around Number 90 upward, mostly use my original styles.
Typical examples of a dedicated Bass Line can be found among the Beatles songs : numbers 137, 'All My loving', 142 'Eight Days a Week', 151 'Michelle', 156 'Something', 150 'A little Help from My Friends' and a particularly good example is, number 154 'Penny Lane'.
It should be noted that most of the Variations in these Styles, use either 8 measures or all 16 measures available, since using the usual 2 or 4 measure Variations, would have been too repetitive and would not allow the full scope of a dedicated Bass line.

The option which allows you to FIX the Bass line notes - irrespective of which Chords you play in your Left hand - and indeed the notes in any of the other component parts of the Composer style, can be found in the Composer Editor. This can be useful if you wish the Bass Line to play a series of so called 'Pedal Notes' during all or part of a Variation. For example, You may wish the Bass Line to play a series of just 'C1' notes while your Left Hand chords play a riff such as, Cmajor, Dm7, Em7, Dm7, Cmajor............... Assuming that the Bass part just contains a series of 'C1' notes on the 1st and 3rd beats of each measure, if left to the normal Auto Accompaniment process, the Bass Line would probably play C, D, E, D, C.......... which may not be what you want! Try getting a realistic Bass line for 'Tuxedo Junction' on any of the Built-in Big Band styles!!

You will find this 'Magic' option here : Program Menus > Composer > Record Memory (A, B or C whichever you wish to work on) > select a Variation > OK then 'Chord Modify Change'. Move the Red cursor over the BASS part (if it's not already there) and in the Second column, change the entry to 'SPECIAL'. In the Third column, change the entry to 'THROUGH'. The 'Function' column will then show 'CHANGE'. Press 'OK' to confirm. Carrying out this procedure, will force the Auto Accompaniment to play exactly, all the Bass notes which you enter into the BASS track of the Composer, when building the Style, using either Step Time, or Real Time recording. Note that this will affect EVERY single note in the Bass part.

If it is desired to only have certain notes, or groups of notes 'Fixed' and the remainder of the Bass part determined by the Auto Accompaniment, then this can also be achieved as follows : Do not change the option in the 'Chord Modify Change' for the entire Bass part, as described above. When you enter the notes in the Bass part of the Composer Editor, you will see at the bottom of the Step Recording Page, a small rectangular window which contains the data for every Note in the Bass part: i.e. NOTE (Pitch), VEL(Velocity), LEN(Length) and under CHORD MODIFY, (GROUP and TYPE). For each Note in the Bass Part, the GROUP and TYPE parameters can be altered to one of 23 different responses, to the Chords which are played in the Left hand. The option which allows individual notes within the Bass part, to be played 'as written', irrespective of the chord played in the left hand, can be selected by setting the GROUP to 'SPECIAL' and the TYPE to 'THROUGH', for the specific notes. Notes which are not set to 'SPECIAL'/'THROUGH' will follow the Chords in the Left hand, as determined by an alternative Chord Modify setting