Against the backdrop of a continuing decline in CD sales, U.S. record labels have also privately worried that track downloads could also finish in the red this year—for the first time since Nielsen SoundScan started tracking the format in 2004.

But for the first time since the week ending March 14, year-to-date track sales are larger than the corresponding period last year. For the week ending June 6, year-to-date track downloads totaled 510.6 million—up 0.2% from the 509.6 million units for the corresponding period of last year, according to Nielsen SoundScan.

Year-to-date sales had been consistently ahead of last year in the first 10 weeks of 2010, but only marginally, leaving label executives worried about the meager growth. Then things began to darken between March 15 and June 6, when year-to-date track downloads were less than last year’s total.

The comeback has apparently been fueled by hit songs. With the exception of the period between Christmas and New Year's, it's unusual to have more than two songs selling more than 200,000 tracks. That holiday shopping time spans one or two sales weeks, depending on how the calendar breaks.

But in the last five weeks, there have been at least three songs selling more than 200,000 every week. In the week ending May 15, four songs attained that milestone.

In the most recent week, which ended June 6, Katy Perry’s “California Gurls” featuring Snoop Dogg scanned 318,000 units, while B.O.B.’s “Airplanes,” featuring Hayley Williams, had 248,000 scans. Usher’s “OMG,” featuring Will.I.Am, garnered 226,000 units.

During those five weeks, Eminem’s “Not Afraid” was the other hit on the Digital Songs Chart to top the 200,000-unit mark.

Meanwhile, digital album scans year-to-date are up 13.8% to 35.6 million from 31.3 million in the corresponding period last year, while CD album sales are down 17.9% to 98.8 million from 114.3 million. That leaves overall album sales down 11% to 130.6 million, from 146.6 million units.