Don't think they have a great collection and I haven't bought any tracks from them yet; but from browsing around a little bit, there are a few tracks from $0.99 (https://one.ubuntu.com/music-store-up/release/2135907/osvald…). They also have an iPhone and Android app.
If you wish to give me some free storage, please feel free to use my referral link: https://one.ubuntu.com/referrals/referee/3709467/
From the website:
How can I get 6 months free?
Buy any track from our new Music Store, and you will get 6 months Music Streaming + 20 GB storage free and will be added to your account immediately after checkout in the Music Store. The subscription will automatically stop after 6 months, unless you choose to renew it for $3.99 a month or $39.99 a year. This offer is for new subscribers only, and it works with any purchase from the web Music Store or Rhythmbox plugin.
Is the "Music Streaming" just cloud storage where you can access your music files? Or does it work similarly to Spotify/Google Music. Get confused when it says Music Streaming + 20GB Cloud storage :/