The Mystery Of The AC97 Sound...

[Blomberg]

MIDI support isn't a part of AC97 at all

I will not dispute that, as I don't know much about AC'97 as a standard.
I use the MIDI in (joyport thingy) of a VIA 686b with AC'97 on a daily basis, and it does the job fine for me.

My quarrel with this chip is the audio quality. When cranked up high, it creates noise. This is not a problem for 'normal' users, though, unless you do recording or are just picky with your audio  :-D
Compared to other AC'97 solutions, this is certainly one of the better ones (or maybe I was just lucky with my mobo  :-) ).

I intend to get myself a 24bit, high quality sound card at some point (for my PC), but these most often come without any MIDI functionality at all, so the VIA chip will continue its duty in that particular area, it's quite adequate.

[Blomberg]

If you want to use the 686B as an instrument itself, it's probably limited to FM synthesis or software rendering (no idea, too lazy to look up the datasheet)... Something like an SBLive (whatever model includes the onboard RAM) has the power to replace actual MIDI instruments (if you have the software to program the wavetable(s) and whatever nifty DSP transforms can be run on them), but may not be perfect for pro digital-out/waveform use if you're stuck with the 48KHz issue.

I only use the controller part of the VIA MIDI, as I came to the conclusion some time ago, that all sound cards builtin MIDI sounds are crap by definition  :-D
I just use it to send events from my keyboard into the computer, for use with virtual instruments, soft samplers etc.