The Gravis UltraSound or GUS is a sound card for the IBM PC compatible system platform, made by Canada-based Advanced Gravis Computer Technology Ltd. It was very popular in the demoscene during the 1990s. The Gravis UltraSound was notable at the time of its 1992 launch for providing the IBM PC platform with sample-based music synthesis technology (marketed as "wavetable"), that is the ability to use real-world sound recordings rather than artificial computer-generated waveforms as the basis of a musical instrument. Samples of pianos or trumpets, for example, sound more like their real respective instruments. With up to 32 hardware audio channels, the GUS was notable for MIDI playback quality with a large set of instrument patches that could be stored in its own RAM. The cards were all manufactured on red PCBs, similar to fellow Canadian company ATI. They were only a little more expensive than Creative cards, undercutting many equivalent professional cards aimed at musicians by a huge margin. Versions UltraSound (Classic) The first UltraSound was released in early October 1992, along with the Gravis PC GamePad. The Ultrasound was one of the first PC soundcards to feature 16-bit, stereo. The final revision (v3.74) of the GUS Classic features of onboard RAM (upgradeable to 1024 kB through DIP sockets), hardware analog mixer, and support for 16-bit recording through a separate daughterboard based on the Crystal Semiconductor CS4231 audio codec. Reception Computer Gaming World in 1993 criticized the UltraSound's Sound Blaster emulation and lack of native support in games, stating that "it is hard to recommend this card to anyone other than a Windows MIDI musician". UltraSound MAX Released in 1994, UltraSound Max is a version of the GUS with a CS4231 codec on board, 512 kB of onboard RAM (upgradeable to 1024 kB with a single SOJ chip), and Panasonic/Sony/Mitsumi CD-ROM interface slots. CS4231 provides support for Windows Sound System specs, although the IO port range doesn't match the WSS hardware, and can be used for SoundBlaster emulation. The software CD includes a demo that featured "3D holographic sound" through the use of software HRTF filters. UltraSound Plug & Play (PnP) Released in 1995, the Ultrasound Plug & Play was a new card based on AMD InterWave technology with a completely different sound set. Supposedly Synergy acted as the ODM-producer for it (as evidenced by their logo on the rear side of the card, although early and now