If you're asking is it possible to have one app play both videos and audios, then yes that's pretty easy. If you're asking can you play audio from one source simultaneously with video from another source, then no I do not believe that is possible.
I could help, but it really is pretty trivial. It looks like you have all the pieces already. All you need to do is instead of calling showVideoScreen(), set all the parts of a "song" roAssociativeArray, set up an roAudioPlayer setting the content to the "song", and then call Play() to start the audio. You might want to have a different details screen for audio vs. video with a Play/Pause button instead of Resume/Play from beginning.
Is there any specific part that you don't understand?