there's a few ways to approach the abstract, whether you're trying to do microsound thing where there's short glitchy samples making up a repeating pattern giving context to a beat or the more ambient scene.

I will say that its hard to do on purpose. Most of the stuff you might listen to was done by randomization.

I use Reaktor quite a bit for this. Lots of great granular samplers and noise machines.I haven't gotten into Max/Msp, but alot of the abstact guys use it. i'm pretty sure that's what Murcof is using to mangle samples.
One freebie that might be of interest is Gleetchlab..

http://www.gleetchplug.com/gleetchplug/labvideos.html

version 2 is still free. the videos are of version 3 that's coming out soon but give you a pretty good idea of what's easily capable with it.

there are also some free Max patches around that rock like Cameltoe which was designed by Twerk.

The field recorder is a great idea. I carry one around quite a bit. catch random sounds.

There are also a number of free plugins that do some atypical stuff like Livecut and Glitch (if you're on a pc).

actually, you bring up am interesting thing here. While most of what you're listening to is algorithms and automated modulation, I've come up with a few techniques that approximate certain abstract sounds using nothing more than a 404.

Frozen reverb---Some reverbs have a "freeze" switch that loops the tail endlessly (ala Ableton), but this can be done with any pad sound. Apply reverb to it, all the way to wet and resample a short 1/8 or 1/16 note with loop turned on.

Clicks and Cuts method---General you can just line up samples and attach an lfo to randomly pick a new start position every 1/8 note and end up with something interesting. With a 404, you're going to have to chop individual sounds, but it can be fun. Have a decent length sample (you could even drag the 404 around with the onboard mic on around the house banging on different things and talking into it.) then as you're going through the sample hit the mark button twice really quickly at random. resample that sound. do it again and again. you can resample with different effects on if you like. Move the effects knobs when resampling to create movement in the sound. I think the shortest sound a 404 can record is 30ms, but that should be good enough for this. the trick with weird percussion is to have something "normal" pulse throughout...maybe a kick on 1 and 3 to keep it steady. not required, but some aren't into Autechre.

Granular method---this spirals out from the last technique. if you don't have loop capture this gets trickier because you can't make a pattern and resample different effects on it. you could make a "pattern" by just recording freehand via resample though. Anyways what you're looking to have is a variety of short looping samples. If you want a more ambient approach, make the loops longer. then add the panner to get the "grains" to move around a bit. resample. then add a bit of delay(the tape echo works best as you can change the delay time without clicks). resample. layer some reverb on top. done. this is good for approximating the Murcof sound.

if you have specific audio, i could help with strategies for accomplishing it.

some good tips brett, just watched some of the videos on the gleetchlab site and it looks fresh. i also picked up an ensoniq eps not too long ago to mess with as well, but don't really have the space to set it up at the moment...if only i could come up on the rack mount version...

for sure, brettweldele. this is good stuff. i am actually pretty set up for making glitchy stuff. i resample things with a shifting mfx 23 on it, then 'mark' things into tiny cuts, and make patterns out of those (or sometimes make loops with cuts layered in during resample). i sometimes use audiomulch on things before recording in.

i was looking more for the sound-source ideas from earlier in this post, and any info on how people are doing their arrangements with field recordings blended in.

i bring up murcof cuz he and his little gang do an interesting mix of the glitch and field recording in some of their tracks. as you say, a pulse on 1 and 3 can be awesome.

good stuffs guys.