Taylor Swift on Sunday took another swing at online streaming services, this time taking aim at Apple by keeping her platinum-selling album "1989" off the new streaming service.

In an open letter to Apple, Swift criticized the tech giant for its three-month free trial period in which musicians won't get paid. The cash-rich tech firm, she said, should cover the costs of the free trial and pay artists, producer and writers during the period.

The 25-year-old musician and songwriter is quickly becoming a leading voice for artists' rights. Last year, she wrote a detailed op-ed in The Wall Street Journal about her concerns over free streaming and other online business models that devalue the work of musicians.

On her Tumblr post "To Apple, Love Taylor" posted Sunday, she explained that artists shouldn't have to shoulder the burden of Apple's promotional costs.

"I find it to be shocking, disappointing, and completely unlike this historically progressive and generous company," Swift wrote.

"We know how astronomically successful Apple has been and we know that this incredible company has the money to pay artists, writers and producers for the 3 month trial period… even if it is free for the fans trying it out," Swift wrote.

The decision, just months after she pulled her work from Spotify, may ultimately be a minor setback for Apple. Spotify has thrived since Swift pulled "1989" off the service; it doubled the number of paying subscribers to 20 million over the past year.

But Swift's criticism of Apple can hurt the company's image, especially as other musicians and artists join her call for greater compensation from online music services.

Apple Music will launch June 30 with a monthly $10 streaming subscription plan that sets in after an initial free trial. Apple will also offer a free Internet radio service and continue to sell downloads of songs and albums through its iTunes store.

Spotify offers free ad-supported music streaming and charges $10 a month for ad-free listening and access to songs on-demand.

Apple declined to comment for this story. 

[Taylor Swift takes on streaming music]

Beggars Group, an independent label that represents Adele, Queens of the Stone Age and White Stripes, is also angry about Apple's free three-month period.

"Whilst we understand the logic of their proposal and their aim to introduce a subscription-only service, we struggle to see why rights owners and artists should bear this aspect of Apple’s customer acquisition costs," Beggars wrote on its Web site.

Swift hasn't been hurt by her decision to keep off Spotify. Sales of "1989," even CD sales in physical retail stores, have soared. 

But in the open letter to the company posted on Tumblr, Swift said other musicians, writers and producers are afraid to speak out against Apple because of its enormous consumer reach.  

"But I say to Apple with all due respect, it’s not too late to change this policy and change the minds of those in the music industry who will be deeply and gravely affected by this," she wrote. "We don’t ask you for free iPhones. Please don’t ask us to provide you with our music for no compensation."

[Jay-Z, Madonna and friends offer expensive Tidal service]

[How Apple's streaming service compares to what's already out there]