A free program for Android, by Orho Tech.
The Duo Audio Player app for Android is an audio player that allows you to listen to your favorite songs at the same time on both your Android phones or tablets.
The app is completely free and works on both Android phones and tablets. You can listen to music on both sides of the stereo using your Android device’s built-in speaker or earbuds. You can also use the app to listen to music on your Android device.
Duo Audio Player works as a virtual turntable, so you can change the speed of your music by going back and forth. You can also skip to the next or previous track.
You can also listen to two songs at once with the option to choose which one you want to listen to at a time.
Duo Audio Player supports a wide variety of music file formats.