"So what software synth would you suggest? I think it's a toss up between Roland Virtual Sound Canvas and Yamaha S-YXG50."
When it comes to system stability on WinXP, I would have to say that the Roland Virtual Sound Canvas v3.23 will lead to the occasional BSOD when running under WinXP due to some deficiency in the device driver coding. It might be stable under Win9x, however. The Roland Virtual Sound Canvas v3.23 sound is somewhat close to the real Roland synth hardware, better that the Microsoft GM/GS soft-synth which licensed Roland Sound Set digital samples.
I believe that the VSTi or DXi plug-in versions included in the VSC-MP1 package do not use a device driver and appear stable for now - however they default to the SC-88pro waveRom sound set. You would have to rename one of the other SC-55 or SC-88 tone sets to the RVI01.DAT file-name to try the older sound maps. The Roland VSC v3.23 is very good for previewing or quickly converting MIDI files to Roland-flavored WAV files, uses MMX instructions in the driver and SSE instructions in the VSTi and DXi versions - but BSODs because of the VSC.SYS WinXP device driver faults, that just does not cut it in 2008 with a product that was last updated for Win2K/XP in 2003. Plus, Roland of course cripples their VSC softsynth (just like Yamaha) by making the compressed waveRom samples much smaller that those waveROMs included with their respective hardware synths.
To gain system stability under WinXP, it is possible to use the Roland VSC v3.23 included VSTi plug-in version of the Roland VSC sound set with the following tools:
1.) The SAVIHost single VSTi by Herman Seib
2.) The Maple Virtual Midi Cable by Jeff Hurchalla
Basically you have to install the complete Roland VSC v3.23 package, just to install the v1.00 VSTi VSC.DLL file. There is a Roland update to VSC.DLL version 1.01 available. Use the Maple Virtual Midi cables to redirect the WinXP MIDI stream to the SAVIHost instance of the Roland VSTi and you are in business without the WinXP BSODs. This does mean manually starting (or a batch/script file) the SAVIHost Roland VSTi instance and redirecting the Windows MIDI output before starting said Dosbox hosted game. Remember that the VSTi implementation does default to the SC-88pro waveRom sound set.
The Roland Virtual Sound Canvas Multi-pack (VSC-MP1) CD-ROM is still sold by music instrument/device re-sellers such as Sweetwater. The VSC-MP1 does not appear to be available as a pay download.
As to the Yamaha S-YXG50 v4.23.14S WDM 2MB WaveRom version, it seems to be available sometimes on eBay, or as VOGONS member Zup indicated in the game Final Fantasy VII. The typical version has Yamaha 2MB compressed WaveROM files. Unless an update is performed to bring the Yamaha SXGXGWDM.SYS driver to version 5.13.2600.3 you will have BSODs under WinXP.
At some point I found the updated Yamaha 4MB waveRom files as part of a demo version of SOL2 on the Yamaha website. Still had WinXP BSOD crashes with the Yamaha SXGXGWDM.SYS driver version 5.13.2600.2 (Oct 5, 2001), then a few years ago, by a file drill-down search accident I found two buried Microsoft CAB file updates which fix the BSOD problem in the Yamaha SXGXGWDM.SYS driver file AND includes as a plus the Yamaha 4MB waveRom files! The new driver is version 5.13.2600.3 (Nov 27, 2001) and the WinXP BSODs seem to go away. The Yamaha S-YXG50 version found on the Internet or shipped with FF VII will BSOD, the Microsoft CAB file updates corrects the BSOD problems under WinXP.
OK, here are the direct links to the Microsoft CAB files which update the Yamaha S-YXG50 v4.23.14S WDM soft-synth to be stable under Windows XP (SP2/SP3). One links to the CAB update for a 2MB WaveROM/driver/DLL update. The other links to the CAB update for a 4MB WaveROM/driver/DLL update. I would recommend downloading these fairly soon as Microsoft probably does not realize that these two Yamaha update CAB files are still available on their servers. 😀
Microsoft download CAB update files for Yamaha S-YXG50:
Yamaha S-YXG50 v4.23.14S WDM 2MB WaveROM update: MU50 2MB V2.0
Yamaha S-YXG50 v4.23.14S WDM 4MB WaveROM update: MU50 4MB V2.0
You might wish to use extraction software such as Universal Extractor to extract the update files from the CAB files. There is a SXGXGWDM.INF file for installation of the updated files.
Now for how the two soft-synths, Roland and Yamaha sound in game as compared to hardware synths, real and emulated SoundBlaster audio cards and real and emulated Gravis Ultrasound audio cards. For your listening pleasure here are seventeen audio/audio-video examples of the possible selections for 'music cards' in the audio configuration of the 1994 DOS game SYSTEM SHOCK, to include both soft-synths under discussion. The example XMIDI file is the Introduction theme to SYSTEM SHOCK. Many of these audio files were graciously provided by forum member 5u3 The audio/AVI samples are to be found in links contained in this post at the QuestStudios forum.
Best of luck,