Kankichi-kun (かんきちくん) is the official name of the music software developed by Nintendo of Japan.
According to composers who used the software, the program operated in a similar fashion to a MIDI sequencer. The program ran on a Sony NEWS computer. However, composers who used the driver outside of Japan had to write the music in assembly.
Composers could make their own instrument samples using a program called Tako Sample (タコサンプル). Tako is Japanese for Octopus, and it is most likely named after the 8 sound channels that the SNES provided.
Kankichi-kun was used not just by Japanese developers, but was also used by American and European developers as well, each with their own modifications. As a result, there are many, many variants of the driver.
While the sequencer itself has not been released, there are some games that used its source code (Top Gear, for instance), which have had their source code released. Some of the source files are called KAN.ASM, no doubt referring to the program's name.