I purchased an SD5 when they were first released and sold it a week later. I was very disapointed with the Riff mode. I was expecting it to work like Dan indicated, that it would develop a riff based on the precious chord changes in the song. What I found was that it played a set pattern of chord changes based on the last chord you played before you hit the riff (variation 4) button. It would play the exact chord changes every time regardless of the chords used in the song.

There was an organ-blues style where the riff pattern sounded good because it was a blues progression that fit with most songs that I would play with that style. On many styles, riff chord progressions did not fit with the chord progression in the song and it sounded terrible.

The other item I was disapointed in was that the SD5 did not have a "to end" button like the SD1 has. I like playing my own endings then hitting a simple one measure ending to end a song. I am not sure why they eliminated this feature.

Other then the above issues, I thought the SD5 was a good keyboard.