Of course, to do this you need some kind of "tool". Like a hardware or software DAW. But the MB-SEQ seems to be the ultimate tool for creating step sequenced bass, melodies, drums -- anything really!
For the OP, you can buy nearly everything you need for SEQ via SmashTV's webshop: http://avishowtech.com/mbhp/buy.html
You assemble modules likesuchas DIN, DOUT and CORE32 then link them with ribbon cables. You then need encoders, knobs, buttons, LEDs and two LCDs. The hard part IMO is making a panel and user interface which looks pretty and works straight away. It's not impossible, but because the different components have different heights, you need to layout everything on veroboard and add spacers to make it all level.
Fortunately there is a solution which has been very kindly "ready-made" by Wilba. Basically everything needed for the SEQ is mounted on one board, including a full control surface. Also, the shift registers which scan buttons or encoders, or drive LEDs are multiplexed together, meaning you need less of them.
This is certainly the easiest solution and the one I am pursuing after having most of my components for 2 years and not getting the darn thing finished! :whistle:
The only trouble is the PCBs are not widely available. This is due to people having actual lives and not spending all their time helping others on this forum. I have my panel in the post from "julianf" and will jump on a PCB when I see one. One day I'll be done too :)
If there's any other info you need, try searching this forum or uCApps first. You'll learn a lot this way.