Jim, I agree with DonM. You just have to know the styles that are available and what songs they are suitable to perform with that specific style. Then it's just a matter of going to that style, selecting it and pressing the synch start button and you're into the song. I created a very extensive music finder directory several years ago, about 750 of the most popular songs I performed over the years. The MFD allows you to save some of the favorites in a favorite area, and select songs by tempo, style, genre, and song title, all of which are great tools when you have a full dance floor. By using the MFD, I can actually transition from one song to another while that first song is ending, thus zero dead time between songs. I rarely use midi files or pre-recorded MP3s because of the time constraints. During a one hour performance, I may use up to 20 different styles, of which, half may be third-party, song specific styles. A couple years ago, I posted a video of how I use the music finder directory on the PSR-3000 and just how easy it was to go from one song to the next, and also in that same video, I demonstrated the use of the MFD in conjunction with registrations. It is very easy and very effective.
Now, I just fired up the PSR-S950 to try and determine what the problem was with the OP, which I may have a solution for. When I select a midi file to play and that file begins playing, if I use the scrolling wheel to find the next file I wish to play and use the enter button, the next feature is activated. However, if I just press the button next to the midi file, it cuts out the first midi file and begins playing the second file. Not having a Genos to try this out, I'm only guess this is a solution, but it may not work on the Genos.
Good luck,
Gary