since you can't have a pad looping on the 404 as you try to record ext. source on, i bought two sets of RCA cables and plug LINE OUT to my computer and LINE IN to my drum machine. then i load up Audacity (free) and just loop my pad on my 404 turn on ext. source and use my drum machine to record drums right over it. now i have a loop with drums recorded onto my computer!

i imagine this will be super helpful for people using a synth and want to record the timing perfect with your loop.

that's why you buy a second sampler