Since there are no obvious markings beyond what's on the chips, my uneducated guess is that it was taken from a "Music Machine" of some sort, like a Karaoke box or Karaoke terminal or maybe even some sort of gaming system - not an arcade game, but something like a slot machine or other such devices - found in Asia or elsewhere. Such devices would use generic low-end mass-manufactured wavetable cards like that.

After using the card and studying it a bit, here's what I found:

First off, I'm going to call this card the Usound MIDI CSG... until the real name is discovered.

Volume and equalizer settings can be controlled using the same files that the Serdaco Yucatan FX supports (https://serdaco.com/downloads/YUCATANFX/). This is similar to all other Dream SAM9733 wavetable cards (at least the ones I own). However, unlike the other SAM9733 cards that I own, the Usound MIDI CSG does not clip its audio output by default.

To my untrained ear, it sounds like it is using a 4MB ROM since 2MB and 1MB ROMs usually sound more compressed. Using the YMedium.mid preset file on all the below cards to keep the comparisons fair, here is is my subjective list from best to worst sounding:

1. Serdaco Yucatan FX -- best sounding
2. Diamond Monster MIDI -- almost a good as Yucatan
3. Usound MIDI CSG -- almost as good as Diamond Monster MIDI, though instrument 40 (Synth Bass 2) sounds a little muffled
4. Miditemp DS-48 -- a larger drop in quality but still overall good. Instrument 40 (Synth Bass 2) sounds twangy and... ugh

On the more technical side, I did some light reverse-engineering on the various jumpers.

• JP1 (1x4)
  • Pin 1 = Audio Out Right
  • Pin 2 = AGND
  • Pin 3 = AGND
  • Pin 4 = Audio Out Right
• JP2 (1x4)
  • Pin 1 = 12 V
  • Pin 2 = AGND
  • Pin 3 = AGND
  • Pin 4 = 5 V (from the 5 V regulator for analog power)
• JP3 (2x3)
  • Pin 1 = 5 V (from waveblaster J1)
  • Pin 2 = 5 V (from waveblaster J1)
  • Pin 3 = R7 4.7 KOhm (which connects to DGND), also goes to U1 pin 45 (SAM9733 TEST1)
  • Pin 4 = R2 4.7 KOhm (which connects to DGND), also goes to U1 pin 44 (SAM9733 TEST0)
  • Pin 5 = DGND
  • Pin 6 = DGND
• JP4 (0 Ohm resistor bridges pins 1 and 2)
  • Pin 1 = DGND
  • Pin 2 = U1 pin 46 (SAM9733 TEST2)
  • Pin 3 = 5 V (from waveblaster J1)
• JP5 (0 Ohm resistor bridges pins 1 and 2)
  • Pin 1 = DGND
  • Pin 2 = U1 pin 46 (SAM9733 GND!!!)
  • Pin 3 = 5 V (from waveblaster J1)

There are some hints of an old company named Usound, but barely anything exists in today's pile of information. The current company by that name is absolutely not the same one and is tied to speakers. I suspect that the "Usound" MIDI chip is nothing more than a rebadged DREAM bank chip or some knock-off variant using the DREAM samples, which would explain why it sounds so similar to others.

To my untrained ear, it sounds like there are 3 different ROM samples being used. Namely:

• Serdaco Yucatan FX and Diamond Monster MIDI are one set (ROM chip shows GMS963200-B)
• Usound MIDI CSG is in the ballpark of the above but sounds different enough to be a different set (ROM chip shows SIN98328)
• Miditemp DS-48 sounds very different from the above 4, strongly suspect a different ROM sample set (CleanWave32 ROM chip shows GMS973201-B)

There can be other explanations for why they sound different, but my first suspect is the ROM samples sets.