A simple combination that makes the world's smallest, lightest, full-function synthesizer.

An Axis-49 and a netbook - an Acer Aspire One (about $350 canadian) to be precise, running Windows XP Home SP3.

It is running a pre-compiled executable Max/MSP program I wrote and freely available here. The program takes the notes from the Axis, optionally remaps them, and sends them to the standard microsoft instrument bank (or loaded VSI instrument). It's not fancy, but the latency seems to be very low. The netbook is not fancy, but surely can run any music software (especally instrument packs).

For ease of carrying the two, I "Velcro-ed" them together,

Axis-bottom facing netbook-bottom, to make a single, portable assembly, see below for more details.

Note that the Axis completely covers up the nextbook and the two are easily linked together with a short USB cable.

Operationally it's pretty simple, I tweaked the netbook's power-saving settings to not automatically go to sleep, to not hibernate when the lid is closed, to run in low power mode, and put a short-cut to the AXiS-49 playing program in the start-up folder.

To start, either pull the two apart or just put the Axis-and-netbook down still attached together, with the Axis key-side down, the netbook is then facing up. I flip open the netbook, turn it on, close the lid, and flip the assembly over, putting the netbook top-down and the Axis keys-up.
45 seconds later I check the keyboard plays, plug in headphones or a portable speaker, and I am good to go. (The netbook's speakers are horrible, but so what). The netbook does not seem to be unduly drained by the Axis, and the setup us good for 2.3-3 hours.

How does it sound? There's two levels to that question.
Functionally, with just the Windows default instruments (piano-like sounds) not hot, but OK for playing for practice.

For serious sound, I have the new Garritan Aria-based GPO sound pack. The sound in headphones is excellent. 

Attaching together for carrying a practice setup around

Here is how an Axis-49 is mated with it's netbook.

They are velcroed together, bottom to bottom, with velcro strips at the end. I also got a less risky, shorter "right-angle  USB cable from Firewire USA, it worked out well, although i had to use an elastic band to bend it in a u-turn to shorten the cable.
I found I was generous with the velcro, about half the velcro shown will work fine.

The velcro strip near the middle hold it down so it doesn't slip on tables and such when mounted for performing. 

The black object is a portable speaker. 

Hang-ups with Using the Axis-49 as a jammer

Layout of the keys
1)       the W/H layout can be as little as only 6 notes wide - 6 whole tones, but it can be a wide as you want so in theory one can make do with only 6, but more is better, up to about 12 or so.
95% of the notes in the simple pieces I'm practicing on are with the major/relative minor scale, so on the 7-key wide axis, I can play C, G, D (0, 1 or 2 sharps) or F, Bb, Eb, and kinda play Ab and Db (0, 1, 2, 3 or 4 flats)- the latter two don't really have enough of the important minor notes available. Some arrangements like the tri-tone, others seem to play the sub-tonic and the 7th a lot.

I'm staying on the notes as written, in the proper key, on the grounds that it may train my ear a bit better. Its getting to be somewhat automatic to finger the alternative notes if they are on the opposite side. This is the kind of thing the brain's kinesthetic sense handles easily.

This suffices for practice. I have a semi-tone shift up and down option - I had one with my hand-made jammers and found that I could read a C# score and a Db score fairly just fine with a semi-tone shift, pretending they were in C or D.

I find that in practice, a 7x7 array works OK - note that even a 6-6 would do, but a 7x7 is better.  The other bank is not very useful, unless i want to work out the left hand fingering - I'd much rather mirror image the bank, and use the same fingering for the left hand as the right. I've tried mirror-keys on my earilier jammers and it is indeed good.
 
Each row is a whole tone scale, and an octave is therefore 6 tones wide. The notes therefore wrap on the 7th note-column. The 7th column adds flexibilty.
Most notes played cluster around the major scale,
 
Without note shifting I can play in C, G and D. F, Bb, and Eb,  Ab and Db are a bit of a stretch, because you lose easy access to the more important minor notes, and the hand has to (horrors!) actually move to play them.