Alan, for me it all boils down to knowledge of the songs and styles that I have available. For example, in the movie Road House, there was a song that I really enjoyed, Hoochie Coochie Man. I downloaded the lyrics and chords from Ultimate Guitar Tabs, then downloaded the song from You Tube and converted it to an MP3. The next step was to go through the PSR-S950's onboard styles and find something that would be suitable for the song. The very first step to this is to select any style, makes no difference which style as long as it has the same beat, then, while listening to the song, use the tap tempo and synch the keyboard with the song's tempo.
Next, I just start going through the styles in the genre of the song, in this case R&B, and when I find something close, I then go through the variations to determine which ones would be suitable, then determine how to fit in the breaks, fills, multipads, and right hand comps.
Once this is completed, then I work on the vocals, and using the transpose button, figure out what key would be in my comfort zone, then do a couple practice runs to get the inflections and phrasing correct. If it all seems to come together, I usually load the information into my Music Finder Directory so it can be instantly recalled at a later date.
The final step is to record the song as a one shot deal using the keyboard's onboard recorder. This gives me an idea of how the song will sound when performed live, which for me, was the most important aspect.
Granted, this may seem like a lot of work just for one song, but when you are a full-time entertainer you want every song to sound professional, and as close to the original as possible.
At one time, I had nearly 4,000 songs in my aging brain and the settings for them were stored on USB drives and floppy disks - it was an insane number to work with. I finally whittled that down to just over 750, selecting the best songs to dance to, and songs that would be instantly recognized by most of my audiences.
For those folks that have downloaded the contents of my USB drive, they will find all of the styles I worked with in addition to those in my PSR-S950. Many link directly to the MFD, therefore, if they were to load my MFD from the USB drive into their keyboard, they would benefit from all the work I put into creating my custom MFD for the S-950. And, I believe it will transfer to most other PSR arranger keyboards, at least the newer models.
Hope this helps,
Gary