Aria Chipset SPU

The Sierra Semiconductor Aria sound chipset was used in 1st-party Aria sound cards as well as being licensed to makers of other units.

It had a large list of features
32 Simultaneous voices
FULLY General MIDI compliant
Fully AdLib and Fully SoundBlaster compatible
Joystick Port
MPU-401 UART MIDI Port (no need for an external MPU-401)
Full Duplex
16-bit DAC
-70 dB max mixer noise
Parallel processing 42 MHz DSP chip (simultaneous threads limited only by RAM)
Maximum 32 MB RAM/ROM DSP address space
Stereo DAC input, hardware adjustable 3-bit volume. later specs added a 2nd DAC and 8-bit volume
Stereo auxiliary input (intended for CD-ROM), hardware adjustable 3-bit volume, later added a 2nd and 8-bit volume
Stereo external input, hardware adjustable volume, later added a 2nd and 8-bit volume
Stereo external line input (mic in/line in)
DAC output, software adjustable volume 3-bit
10-bit ADC (Diamond Sonic Sound and later specs had 16-bit ADC)
Later units had treble and bass tone control
Some units included speech recognition
Most units had a SCSI controller.
It would show in hardware as up to 5 simultaneous sound devices and could act as more than that.
Somehow, it was sold cheaper than cards with any one of these features.

Support for DOS, Windows 16-bit, Windows 32-bit, OS/2 Warp, and Linux though not all features work in all places; but Adlib and Sound Blaster modes are "bulletproof" on all platforms (theoretically BeOS, UNIX, Amiga, etc...). DOS requires a software MIDI interpreter that is easiest to provide by using DOS Aria drivers. This is not intuitive since simply plunging in the card is enough for most features to work (many users decided not to install the drivers the moment they heard sound from the card)

Three proprietary software development kits were produced (A basic kit for normal use, premium kit with Game API and basic Speech Recognition and other advanced tools for other features, and Listener kit for advanced Speech Recognition) and later all of them became available for free download from Sierra including sourcecode (but everything remains proprietary). However, the Game API included with the premium kit is owned by Dave Corley who does not allow his sourcecode to be redistributed. He can be contacted directly for options to obtain source code.