Sales of CDs in the US dropped by 31.5% in the first half of 2015, according to music industry figures.
Just 41 million CDs were bought between January and June, down from 56.8 million in the same period last year.
But the losses were largely offset by a growth in streaming revenues, which grew 23% to reach $1.03bn (£697m).
Streaming now accounts for one-third of the US music industry's income, which remains relatively flat, with total revenue down 0.5% to $3.17bn (£2.05bn).
Wholesale revenues - which reflects what distributors and record labels actually receive - rose 0.8% to $2.32bn (£1.5bn).
The vinyl resurgence continued apace, amid a surge in new independent record shops.
Sales of LPs grew by 52% in the first half of the year, raking in $221.8m (£143m) - roughly half as much as CD sales.
However the overall value of vinyl was still far smaller than CDs or digital, according to figures from the Recording Industry Association of America (RIAA).
RIAA Chairman Cary Sherman said that the figures showed "the story of a business undergoing an enormous transition."
He also warned that "intense demand and billions of streams does not always equal fair market rates or a fair playing field."
This year has seen increased competition for streaming services with the introduction of both Apple Music, Jay Z's launch of Tidal and Amazon's entry into the market in a bid to compete with the likes of Spotify, Rhapsody, Rdio, Deezer and Google Music.
However, the revenue from digital downloads is still worth more than streaming, totalling $1.3bn (£842,000) despite being down 4%.
Taylor Swift's 1989 was the biggest-selling album in the first half of 2015, shifting 1,328,000 copies (2,011,000 copies including streaming-equivalent sales).
Canadian hip-hop star Drake came second, with 965,000 fans buying a copy of his fourth album, If You're Reading This It's Too Late.
The top 10 also included British artists Sam Smith and Ed Sheeran, as well as the Fifty Shades of Grey soundtrack.