Here you go!
Step 1: A-Pro Hardware 1. Power on A-500Pro.
2. Make sure the Merge button on the left panel is set to OFF.
3. Press the [ACT] button and the left arrow button simultaneously, turn the Value knob and select System Setting > Startup Memory > "LAST ACC MAP"
4. Press the [ACT] button and the left arrow button simultaneously, turn the Value knob and select System Setting > L Function > "L9"
Step 2: A-Pro Editor 1. Launch A-Pro Editor and select "19" from the Control Map drop-down, then press [Receive]. (A-Pro Editor receives Control Map 19 "Sonar ACT Map 2" data from your A-500Pro)
- For non-Sonar users reading this, select any of 01-14 (maps for daws) instead of 19.
2. In the Title field, change the name from "SONAR ACT Map 2" to "Studio One Map."
3. Click B2 and select "Latch" from the Button Mode drop-down and click OK. Do the same to B3 and B4.
4. If you want to use your expression pedal to control a soft synth's modulation (rotary speaker, hihat pedal, etc.), click the Express (P2) and select "Channel Message" from the Assign Message drop-down, "Contro Change" from the Type drop-down, and choose "1" from the Control Number field. Click OK to exit.
5. Go to File > Save As and save the map you have just edited.
6. Select one map that you don't use from the Control Map drop-down (I chose 17 because I don't use SD-50).
7. Click [Transmit]. (A-Pro Editor transmits the "Studio One Map" to A-500Pro and overwrites the map 17)
Step 3: Studio One - Options 1. Launch Studio One 2 and click your audio interface icon shown in the Setup section. (This will open Options)
2. Select the External Device tab and click [Add].
3. Select [New Keyboard] and enter the device model name "Roland A-PRO 1" and the manufacturer name (Roland), then select "A-PRO 1" from the [Receive From] drop-down, and "A-PRO" from the [Send to] drop-down.
4. Check [Default Instrument Input] and click OK to exit.
5. Click [Add] again and select [New Keyboard] and enter the device model name, this time "Roland A-PRO 2," and the manufacturer name (Roland), then select "A-PRO 2" from the [Receive From] drop-down, and [A-PRO] from the "Send to" drop-down.
6. This time, DO NOT check [Default Instrument Input]. Click OK to exit.
7. Click OK and exit the Options menu.
Step 4: Studio One - Control Link 1. Create a new Song (project).
2. Press F3 to open the console. Then click [External].
3. Double-click [A-PRO 2] under the External Device pane that appeared.
4. Enlarge the keyboard window that opened.
5. Click the MIDI Learn button and turn the R1 knob on your A-500Pro. You see a knob appear on the keyboard window. Do the same to all other controls on the A-Pro, in this order if you like: R knobs > S sliders > A pads > B buttons > L buttons (incl. L9)
6. Right-click on each knob (except R1-9) and select the appropriate controller shape (e.g. "Fader" for S1-9, "Button (press/release)" for A1-8, "Button on/off" for B1-4, "Button (press/release)" for L1-9.)
7. Double-click the name under/beside each knob/slider/pad/button and rename like "R1" "R2" if you like.
8. Click [MIDI Learn] to turn it off.
9. Right-click on each L button and assign the following commands if you like:
L1 = Transport - Go to Loop Start
L2 = Transport - Rewind
L3 = Transport - Forward
L4 = Transport - Go to Loop End
L5 = Transport - Stop
L6 = Transport - Toggle Start
L7 = (I wish there was a "Pause" command)
L8 = Transport - Record
L9 = Transport - Click (=metronome)
10. Close the keyboard window.
Step 5: Studio One - Project 1. Load a soft synth (let's use Mojito) onto the new Song. Note that "A-PRO 1" is automatically selected in the Input field.
2. Select "A-PRO 2" from the Focus drop-down (button) on the Mojito's property page if not already selected. And turn on this button that now says "A-PRO 2." (the button gets highlighted in orange)
3. Play the A-500Pro keyboard. The meter on the instrument track responds and you hear the sound from Mojito.
4. Turn the R1 knob. The meter on the track does not respond (this is good, don't worry).
5. Insert Tricomp to the Mojito's bus inserts. Now you see both Mojito and Tricomp on your screen. And only the one currently in focus shows the A-PRO button in orange.
6. Turn the R1 knob on your A-500Pro (the right window in the upper left corner responds). Then turn the big Cutoff knob on Mojito (the left window in the upper left corner responds). Click the bind button between the two small windows.
7. Click the Tricomp property page and, again, turn the R1 knob on your A-500Pro, then turn the big Compress knob on Tricomp. Click the bind button.
8. Now you can control the big knobs on the plugins respectively. Do you also wish to use the R1 knob to control the console's Pan slider when the focus in on the Arrange view? To do so, you have to turn off the focus button on the plugin first, then bind the pan slider and the R1 knob the same way.
9. Lastly, don't forget the L1-9 buttons. Make sure they do what they are suppose to do.
That's it. When you use Sonar, Sonar sends map 19 to A-Pro automatically so you'll be using map 19. When you use Studio One, switch off the ACT button and manually select map 17 by pressing the left arrow button until you see "CTRL MAP," then select 17. When you power off A-Pro after using Sonar, switch off the ACT button first (this will automatically switch back the map from 19 to 17) so that the next time you power on A-Pro it will call up the last map used (map 17).
Good luck! :)