One of the more impressive revelations in Pandora's (P) quarterly report last week was the dramatic uptick in paying subscribers. Music fans willing to pay up for Pandora One more than doubled over the past year to top 2.5 million with 700,000 of those coming on during the first three months of this year.

This is not a big number compared to its more than 70 million active listeners. Most of Sirius XM's (SIRI -0.94%) 24.4 million subscribers are paying subscribers. Spotify attracts a smaller total audience than Pandora but has more more than twice as many premium accounts. Google (GOOGL -1.82%) rolled out All Access this month exclusively as a premium platform. 

The market for premium radio is heating up, and in this video longtime Fool contributor Rick Munarriz explains why getting customers to pay up at Pandora is more important than just the subscription revenue.