The big four record labels have less market value than you might think. EMI, which just went private, is worth around $4 billion, and Warner Music around $1 billion. Sony BMG is is a joint venture and so it's more difficult to value, but $5-6 billion is a good estimate. Universal, the largest of the big four, is worth between $8 and $12 billion based on various estimates. In sum the four companies account for only around $20 billion in market cap. For comparison, Apple is 8 times that large.