I came across this document on the Roland website yesterday while looking for GS specs.
http://cdn.roland.com/assets/media/pdf/INFOCUS01_MIDI.pdf
It's Roland's Introduction To MIDI. I found this part particularly interesting, as I did not know this until now.
General MIDI solves this since all General MIDI devices contain the same set
of 128 standard sounds and drum kit sounds, stored in a specified order.
Each product creates these sounds using its own unique capabilities, but the
goal is to make them all sound like the sounds in a Roland SoundCanvas.The General MIDI sounds originally came from Roland’s SoundCanvas
sound module. These sounds did such a good job of meeting musicians’
needs they became the foundation of the General MIDI standard.
I learned about the fact the 128 sounds are standards, but I thought that they were new sounds created for midi. I never know but the Roland Soundcanvas until I read your post honestly. Thanks for sharing the info!
The SoundCanvas was the first General MIDI synthesizer, introduced on the same day that the General MIDI specification was ratified.
Chair of MIDI 2.0 Working Group