Call Music is an Android app developed by The Matrix that plays a melody on outgoing and call-waiting phone calls. The app offers a Caller Ring Back Tone for free, allowing users to customize the sound that plays for their callers. The app also includes a wearable feature that makes the user's watch vibrate differently in the same situation.

Call Music is a useful app for those who want to add a personal touch to their phone calls. The app is easy to use and offers a variety of ringback tones to choose from. Additionally, users who enjoy this app may also want to check out The Matrix's other app, which announces the caller's name during a second call event.

It's worth noting that the app is free to use, but users should review The Matrix's terms of service and privacy policy before downloading. Overall, Call Music is a solid choice for those looking to customize their phone calls with a unique ringback tone.