Music recommendation service Pandora is to begin issuing key audience metrics on a month-to-month basis, as it looks to attract more advertising revenue in the wake of its latest earnings call.

Yesterday we reported that Pandora’s longtime Executive Vice President of Business and Corporate Development, Jessica Steel, was leaving the company after nearly eight years of service. However, the big news was that for the fourth quarter of the fiscal year 2012, Pandora’s revenue hit $81.3 million, up 71% on the same period the previous year – but revenue doesn’t equal profit.

As Reuters notes, it seems that the bigger its audience gets, the more it must pay record labels in licensing fees, which further curtails its journey into profit-making. Whilst half-a-billion dollars was seemingly knocked off its market cap with this announcement, Pandora aims to turn the ship around by throwing impressive monthly audience numbers at advertisers.

“Pandora is the leader in Internet radio, mobile and cross platform advertising and as a leader in these categories it is important for advertisers to have accurate and timely information on our audience,” says Pandora CEO Joe Kennedy. “Active users, listener hours, and share of total U.S. radio listening are the metrics that paint the clearest picture of Pandora’s growing presence and momentum. Until third party measurement services are in place to provide accurate information on Pandora’s users and usage across platforms, we will be releasing our key audience metrics on a monthly basis.”

For the record, Pandora’s total market share of radio listening in the US was 5.74% in February, an increase from 2.90% at the same time last year. And the total listening hours for Pandora in February 2012 was 975 million, up from 483 million last year.

Whilst it had been reported yesterday that its active listeners had reached 47 million, it has now amended this figure and stated that it hit 49m during February 2012, an increase of 57.5% from 31 million on the same time period last year.

When Spotify finally launched its music-streaming service in the US last July, this cranked the competition up a notch or two and led many to debate which audio platform would ultimately win out. The Next Web’s Courtney Boyd Myers put Spotify, Rdio, Grooveshark and Pandora into the ring, whilst Alex Wilhelm later gave his views on why Spotify is worth more than Pandora.

Meanwhile, check out our Future of Pandora feature from earlier this week, where we interview Pandora’s founder and chief strategy officer Tim Westergren.