San Francisco, Sep 6 : In a bid to woo more users to sign up for its paid services, Swedish music streaming company Spotify is testing to make in-app lyrics a premium-only feature. Several Spotify users noticed that in-app lyrics, which pop up under the playing song, were locked away under a paywall. Instead, they saw only a notification bubble saying, 'Enjoy lyrics on Spotify Premium,' with a link to sign up. Spotify told The Verge the feature is currently in a testing phase. 'At Spotify, we routinely conduct a number of tests, some of those tests end up paving the way for our broader user experience and others serve only as an important learning,' C.J. Stanley, Spotify's co-head of global communications, was quoted as saying. 'We don't have any further news to share at this time,' Stanley added. The music streaming platform appears to be looking to build other kinds of features users might pay for, as the price of Premium, like so many other streaming services, continues to rise. In July, Spotify announced to raise its premium subscription prices across a number of markets around the world. In the US, Spotify's Premium Individual plan now costs $10.99, up from $9.99, and the Premium Duo plan has increased to $14.99 from $12.99. The Premium Family plan is now priced at $16.99, up from $15.99, and the Student plan will cost $5.99, up from $4.99. In its latest earnings report, Spotify revealed monthly users of its ad-supported tier had surged 34 per cent over the last year to 343 million. The company's monthly paying listeners grew 17 per cent to reach 220 million. Spotify last month announced that it is rolling out its artificial intelligence-powered personalised music feature 'DJ' to more countries around the world. /IANS