Having worked with it for a few years, modelling music metadata is indeed an absolute nightmare. There are some efforts to standardise this stuff though, see h

Having worked with it for a few years, modelling music metadata is indeed an absolute nightmare. There are some efforts to standardise this stuff though, see http://www.ddex.net http://www.ddex.net which a lot of the digital supply chain is starting to adopt. It's something of a set of scary great kitchen-sink XML schemas (schemata?) but might be of interest to those who get massively nerdy about this sort of thing.