The track-recorders work all the same way. They all listen to inputs A/B and C/D. Have a look at manual p. 48 ff. You decide, which track-recorder will do the recording.

To start a sample once and not restart the sample again you might want to check:

  1. the sample itself is “one-shot” only, it will not loop and stop after beeing played automatically (p. 103, loop mode), AND
  2. you are using a one-shot trig to fire it. A one-shot trig is armed, used, and disarmed automatically (p 80 ff)

Hope this is a little help.