You can listen to your music during your workouts with CardioTrainer's Music Integration feature. Just go to Settings > Music Settings > turn on Enable Music Integration. CardioTrainer uses playlists that you have already set up during your run to play during your workouts, and you can choose the one you want by going to Select Playlist. You can also turn off the music by deselecting "Enable Music Integration."
NOTE: because CardioTrainer uses Android's native music player, there is always the chance that the music player might be force-closed if your system needs more resources. This will stop the music playback, and sometimes start again and stop again as the player is restarted and then force-closed again. To keep this from happening, we recommend reducing the number of applications you are running during your workouts.
If you're using a task killer application (which we do not recommend!), make sure you add an exception for the Music application so it isn't automatically closed.
Unfortunately, CardioTrainer's music integration feature is not compatible with all phones or the newest version of Android, Gingerbread. In most cases, you can still start music in the background with other music applications and then start CardioTrainer.
Even though we still don't have official integration with Pandora's internet radio service yet, it is still possible to use with CardioTrainer. Just start playing a station through Pandora, open CardioTrainer and start your workout. Since the Android operating system gives priority to applications that are running in the foreground, there is a chance that it might stop Pandora from running in the background while using CardioTrainer at the same time. Also, be careful about switching applications when you're tracking a workout; if you switch to Pandora, Android might shut down CardioTrainer!