To set up the SR18 as a slave that records MIDI data sent to it's 5-Pin MIDI input, and follows the tempo of your external device, please follow the steps below...
1. Press the SYSTEM SETUP button.
2. Use the Page up and down buttons to select CLOCK IN then set it to ON by using the VALUE dial.
3. Select MIDI CH by using the Page up and down buttons again, and ensure that it matches the MIDI channel of your external device. You can change the MIDI channel number by using the onboard keypad.
4. Use the Page up and down buttons again to set DRUM IN to ON: V1 with the VALUE dial.
Next, select an empty pattern and adjust its length to match the length of the pattern you wish to record.
Arm the SR18 to record and then play your song on your external device; the SR18 will then record what is coming into it.