The PianoTrax app and the PianoTrax website work together and independently. Mp3s purchased from the website will immediately show up in the app, and vice versa.
You can stream your songs from your mobile device or download them as Mp3s to your computer.
You can purchase an individual Mp3 on the website. With a subscription you can stream all 26,000 tracks on your mobile device and you can download some free Mp3s from the website.
If you have an iPhone or iPad, the PianoTrax app will change key and tempo for you. Android devices will have this feature in a future release.
The app can be used in "airplane mode" with a bluetooth speaker for uninterrupted playback.