Shazam has updated its iOS app to version 7.7.0. The update adds the ability to identify and play any track inside the app using Rdio. Previously users could play any song recognized by the Shazam app, but the feature required opening the Rdio music player separately.
You will still need to have the Rdio app installed on your device and an active account for full track playback to work, but now there is no reason to switch apps every time you want to hear a full song. Rdio is free to download from the App Store. It requires iOS 6.0 or later.