Below are two good music apps that are free today and only for a limited period of time. I discovered these apps through the awesome Apps Gone Free platform and thought music teachers and music aficionados in general will definitely love them.
As its name indicates, this app allows you to easily add video background music either by recording your own voice or through app's track list. The app's editor enables you to customize your music videos the way you want. You can trim selected portions, merge video backgrounds, mark where you want to add music, and many more. Once your music video is ready you can then save it to your camera roll and share it on social media websites like Instagram, Facebook, YouTube, and Vine.