The best alternatives to MusicSource are Jukebox, Rewound, and bop.fm for iOS. If these 3 options don't work for you, we've listed a few more alternatives below.
Rewound is a Music player for your Apple Music library. Easily browse and play your music with customizable on screen buttons and gestures - this is useful for one handed use.
Doppler is a beautifully designed music player designed and built for people who buy music. Import music and playlists to listen offline, and edit song and album artwork and info without syncing. Now with support for Siri, Spotlight Search, and CarPlay.