Hi Bluesguy, on PSR keyboards, editing events for each song track is very tedious.
PSR keyboards are stages of Arrangements. they are so called because they come with rhythmic patterns or styles that incorporate orchestral arrangements, depending on the musical genre.
on the sx900 you can create a song from a particular style, using all sections (Intro, Variation1,2,3,4 and Ending)
You can also use the Chord Loop, or you can use external software.
if none of the above works for you then sell your sx900 and buy a workstation that does not require external software
for example: Yamaha Motif, or Korg Krome.
I hope this helps.
Regards. Hans