I'm not sure about Ocean, but a lot of companies used the Tatung Einstein, itself a 64KiB machine, as a development platform. I would assume that the software used for building this stuff was able to deal with source files larger than the machine can hold. They might've moved onto the likes of Atari STs, IBM-compatibles, and Amigas by the time Wizball was released though.
Plenty of music was developed in the form of source files.
Plenty of music was developed in the form of source files.