Google cannot buy the entire music industry because the music industry is more than the so called major labels. That said, Google or even Apple\Microsoft could buy the all the major labels from their respective owners, if they wanted too. Especially EMI and WMG

Please read:

http://www.nytimes.com/2011/04/11/business/media/11warner.ht...

Warner music group is currently for sale and EMI is available if the right offer comes along.