A simple and common feature which is very important yet which is impossible to do in SP-555 is assigning MIDI notes.

One of the worst cons/demerits of SP-555 is that the PADS RECEIVE FIXED NOTES AND YOU CAN'T ASSIGN MIDI AS YOU WANT unless you use third part software or hardware. Even the fixed notes that you receive are not laid out according to the keys in the keyboard, it is randomly fixed. Know that you have only 16 pads to play with. Neither can you assign the notes to the pads you want nor is it assigned to help you control the MIDI notes comfortable.

If you are planning to buy SP-555 you may like to know this issue and be ready for its limitation. Especially if you want to go beyond sampling/looping in SP-555 and use as a MIDI Controller (since Roland made MIDI in/out available in SP-555) it will totally disappointed you. I've made dozens of request to Roland to check this small software issue for two years but they don't even reply.

The simple fact is that, using SP-555 as a MIDI control sucks unless Roland comes up with an alternative in their next upgrade.

if all you wanted was a device to recieve midi then you should have just got a laptop with ableton live. the drum rack will more than suit your needs

the device was never marketed as the "go to solution for midi controlling your external gear" thats what DEDICATED midi controllers are for.

maybe you should try sampling your drums.