To use the 3 tracks to mute in the manner you've suggested wouldn't require muiltiple midi channels at all. You simply assign the notes that correspond to the 404 pad to the pads on the XR20 in the track you wish it to be in (drums, 1-shots) so when you mute the drums track on the XR20 it mutes the notes triggering the drums on the 404. The gate thing is possible-ish, if the 404 recognizes midi note off messages all you gotta do is make sure the sample on the 404 your triggering is set to gate made, and the sample will gate just like it would if you played it on the 404. The sample would stop when you released the XR20 pad assigned to it. Anything more specific I'd suggest some RTFM as I'm still a bit new to the XR20 and I don't have anything to midi it up to try this stuff out.

You can seldom go wrong with an mpc...i'd stay away from the 500 though. The yamaha rm1x is an awesome sequencer if you're ok with using the sp-404 for holding your samples...just program on the rm1x, hit pattern record on the sp-404 and play it all in to the SP. BOOM... high res patterns captured on the SP's sequencer.

for samplebased stuff, the sampletrak is insane as far as the workflow goes...the sequencer is similar in some respects to the SP-404, but tends to be a lot faster for getting ideas down.

That's a very effective combo indeed. But why have the really tight and full-featured sequencer of the RM1x and then record the patterns into the SP-404 with its overly simplistic sequencer? Doesn't make sense to me. It's much more convenient and versatile to just use the RM1x as sequencer and the SP-404 as sampling sound module. That way you can, for example, mute tracks individually on the fly and lay down complete songs live.

I have ES-1 and RS-7000 and 404

If it were not for the VERY slow cpu on the RS-7000 I would use it all the time. The slice/remix feature is *sick*. The sequencer is sick. Again- the slice/remix feature is just the bomb but you have to wait a long time for samples to load and to process them- and to save back to card- VERY tedious. The slice/remix also works on midi though- and the swing/quantize/editing overall ability of the thing is killer. (odd time sigs, very high resolution midi timing- like over 400/sec vs 96/sec of MPC etc.) I would pay big to be able to increase the horsepower of my RS-7000- I truly would. The synth engine and factory samples blow but oh well.

Here are some very old things I did using both- check "space rocket" for good example of slice/remix feature I used on my guitar.
http://w w wDOTcliffordnoveyDOTcom/ArtandSound/Audio/Audio.html

Now I am looking for the simplest/quickest way to work. I have considered the ES-1mkii for this very reason- you can sample/trim/sequence fast as hell on those things- very fun- and the audio input feature can be very cool too. The mkii is just too expensive for me though at present but would like the better sound quality- 32KHz on the mki gets old after awhile.

The comment on the sampletrack having good workflow has my interest. I am also going to get the 404SX this week.

Cheers-
Om

The reason that I suggested that was to make storage easier. after you're done with your beat, dump it into the sp and back that up- it makes it a lot less cumbersome than trying to maintain an rm1x smf file and stuff on the 404. not only that, but the mute groups and stuff like that on the rm1x can't be recorded in real time to the rm1x's sequencer...which is one of the sad parts of that instrument. make your patterns, compile into a playlist, and then experiment with mutegroups to make some extra fills.

you dont want the electribe for the sequencing you wanna do. i can tell you taht much..