The SP-808 Groovesampler has a built-in Step Modulator. This function is to create synth lines for the internal virtual analogue synthesizer. You can control the synth with a MIDI-keyboard but you can also use this Step Modulator. I’ve created a video with an explanation about the functionality.
Besides controlling the synth you can also use it for slicing samples as an effect. And this function is BPM-controlled so it can give cool effects.
For using the SP-808 in standalone mode you need to have the e-mix studio OS. Check this post about how to upgrade your original SP-808.
Here is the video about the Step Modulator. Enjoy!