On a couple occasions I have tried to use Strum as simple acoustic guitar sound source, but I haven't found a way to disable the strumming function without having it stop responding to MIDI input completely. Am I missing something or is this not possible?
 
 

From page 28 of the full strum acoustic manual

When the Auto-Strum mode is switched off, notes and chords are processed by the chord detection
and voicing modules but the strings are not triggered. In order to play them, one must use the
different strumming keys

and from page 23

Notes with MIDI number ranging between 71 (B4) and 84 (C6) are interpreted as special strumming
keys

and from page 24-25

The strings of the guitar can be played individually enabling one to arpeggiate or create finger
picking patterns. Individual strings are triggered by depressing MIDI notes 76(E5), 77(F5), 79(G5),
81(A5), 83(B5) or 84(C6). These special strumming keys are labeled bass, alternate bass, arp 4,
arp 3, arp 2 and arp 1 respectively. Notes in the chords are triggered by these MIDI notes from
lowest to highest using the following rules:
 MIDI note 76(E5): Bass. always the lowest note in the chord played by Strum.
3.3 Pitch Bend Wheel 25
 MIDI note 77(F5): Alternate bass. When the chord played by Strum is not inverted and
the chord includes a fifth (natural, lowered or raised) then the alternate bass is the fifth. If
the bass is played on the lowest string (sixth string), then the alternate bass will be played
on the fifth string if possible except in the case of the open G chord where it is played on the
fourth. If the bass is not played on the lowest string (played on the fifth or fourth string), the
alternate bass will then be played on the fifth or sixth string. Finally, if the chord is inverted,
or if it does not include a fifth, the alternate bass trigger will play the same note as the bass.
 MIDI note 79(G5), 81(A5), 83(B5) or 84(C6): Arp key 4, 3, 2 and 1. The remaining notes
in the chord are played from lowest to highest note on arp keys 4 to 1 respectively. If there
are fewer than four notes remaining to be played in the chord, the highest one is repeated on
the remaining arp keys. Finally, if the alternate bass is the fifth and if it can only played on
the string on which it is played in the chord, it is triggered by the alternate bass arp key and
it is not repeated on another arp key.

HTH

Strum Acoustic Session actually ships with a manual (I did not think to look for it first) and a quick reference guide which shows all the special strumming keys. It is installed in a folder below the dll in Vstplugins.

Thanks for taking the time, Steve. i looked briefly for the manual, but didn't get as far as checking the vstplugins folder before I decided to just throw the question out. Sort of sounds like I'm out of luck in any case. Kind of surprising that they wouldn't just implement a basic performance mode allowing it to be played like any other synth.

I believe AAS is trying to distinguish the Strum instruments from String Studio, another one of their modeled synths. All of their synths are specialized versions of Tassman.