Shares of Pandora Media (NYSE:P) are trading modestly lower in after-hours action after reporting solid third-quarter results. The stock has more than quadrupled over the last 52 weeks, making a 1.6% off-hours drop look small by comparison.

Pandora's sales increased 50% year over year to $180 million, ahead of the $176 million analyst target. Non-GAAP earnings edged of from $0.06 to $0.07 per share. Wall Street was looking for another performance at the $0.06 level.

The digital radio service's growth drew more strength from improved monetization strategies than from increased market reach. Listening hours grew just 17% year over year on 20% higher user counts; both figures were far below the top-line revenue boost.

Advertising sales held steady year over year on Pandora's traditional computer platform, hovering between $56 and $58 per thousand ad displays, an industry standard metric also known as RPMs. Operating efficiencies increased dramatically on mobile platforms as advertising RPMs surged 47% higher.

In the year-ago quarter, desktop RPMs were more than twice as wide as their mobile counterparts. The gap has narrowed from 110% to 44%. Mobile ad revenue now accounts for more than half of Pandora's total sales. CEO Brian McAndrews gave credit to new or redesigned Pandora apps for iPads and Android tablets.