It may be hard to detect, or the malware may not affect your device. Some malware is specific to working with certain root exploits that are patched on many phones. Or the author pulled the app from the market for some reason.
Either way, the app was removed from the Play Store and the OP is wishing to discuss music apps that do not include apps that download from an unknown source. That issue is just compounded by the fact that a user has to search and sideload the APK.