When MIDI was in its infancy, there was much debate over whether to adopt parallel transmission, which is far faster than serial transmission. However, parallel transmission requires more interconnecting wires between instruments, which leads to much more expensive connectors and can also create ground loop and hum problems. Using parallel transmission would have priced MIDI out of the market for low-cost gear, thus defeating the whole purpose of MIDI as a “universal language.” Another reason is that the computers inside most instruments are incapable of handling superfast data rates anyway; they are pretty preoccupied with scanning keyboards, generating envelopes, running displays, and so on.
