Can confirm both audio and MIDI work perfectly with ALS4000 on NT3.51, though you need to manually configure Midi Mapper for MIDI (FM Synth) to work, which should be straightforward.
However, the particular ALS4000 card I have appears to have issues with audio channels: It only outputs on the right channel, but the sound still feels complete as if it is actually mono. I originally thought something wrong with the jack (such as dirt, lint) and even tried cleaning it after searching online about the audio channel issue with 3.5mm jacks, but it made no difference. The card was fairly cheap and its PCB has fewer components comparing to other ALS4000 sound card pictures I could find on the web, so it might be just the card.
I additionally tried a YMF754 card on my AM3+ system, but not successful. The card cannot be initialized using default settings (which uses INTA# as IRQ), returning an error code 0x0013. Should note that on the same system, the card works correctly (with both audio channels) on Linux and it's original (pre-routed) interrupt was indeed INTA# (pin A routed to xx), according to "lspci -vv".
The Yamaha NT4 drivers are supposed to be usable on NT 3.51, as at one time I tried them on an old Sony laptop (440BX-based) with onboard YMF744, and it got configured correctly. Just that the laptop's built-in speakers do not work on NT3 or NT4 (speakers only works out-of-box on WinME/2K/XP). Probably one needs a 440BX or compatible motherboard to get such drivers configured, similar to its DOS drivers.
AudioPCI NT351 driver (apnt3x86) doesn't work on that system, either. The driver can't detect the card correctly (IO range and IRQ are empty). The exact reason is unknown, though.
I didn't try Aureal cards, but most likely the drivers would not work, as one of the key DLLs imports missing symbol _alldiv. On the other hand, I checked some C-Media PCI drivers (and applications) for NT4 I found online (not sure if they are for CMI8738), and they seem to be okay to run on NT3 (no red symbols encountered in Dependency Walker), though one has to actually check it with real cards.
In overall, it seems NT4 audio driver model is mostly compatible with NT351, but there may or may not be other issues that can prevent drivers from working correctly. Your mileage may vary.
EDIT: Tried one of the CMI8738 drivers I found with my Terratec Aureon 5.1 PCI. PCM audio works correctly, but there's no MIDI support.
EDIT 2: Some inspection of the driver binaries in question, as well as related system logs, revealed something that may or may not be helpful...
- EAPCI driver had a routine that queried for an Intel (0x8086) host bridge but after some fiddling it doesn't appear to be related to the errors. The driver doesn't appear to be able to find the device, with a final error (found in Event Viewer) of ERROR_DEV_NOT_EXIST (The specified network resource or device is no longer available), but in reality the card is present and is functioning correctly on Linux, so unless I could debug the process somehow I won't be able to find out exactly where this error code was thrown.
- YDSXG.SYS seems to require that legacy audio interface to be properly initialized for the driver to be loaded. Looking for the error code I'm having (0x0013) in the driver led me to the MPU401 configuration routine (which generates this error if the port fails). As legacy audio functionality can't be guaranteed to work with newer chipsets... need to find ways to skip the initialization.
(UPDATE: Managed to patch the routine to only init the FM for the legacy part. The driver now installs, but not working correctly. The system freezes as soon as it tries to play audio.)
