This was the reply from my friend who's out there this week. It sounds complicated -- but this is what he said, if it helps.
My understanding is that, if you're going to be working out there, you need a sponsoring employer. The process is then that you fill out an application form for a "Certificate of Eligibility" which then has to be sent via the employer to the visa authorities in Japan. This may take a few weeks to come back, at which point you have to complete an additional form for a visa, which you then have to take to the Japanese Consulate in London in person. Once all this has been done they turn 'round the visa in about a week.
His is a reasonably high profile metal band so maybe they have to do things by the book. Sounds like a proper application for a job, though.
Cheers
Mark