My audience cannot hear my music?

[turritellidae]

Hi, I am using Windows 7 and broadcasting via Procaster of course. Whenever I try to livestream my artwork, I play music from Youtube while I have headphones plugged in. I seem to have all the settings correct for my audience to hear it - the input is set to Speakers' Audio, and the volume is not muted. Whenever I stream, I can hear my music, and the audio mixer shows that it is playing correctly over my channel, but once I have saved the recording and go back to watch the video online, I cannot hear the music. This leads me to believe my audience can't, either. What do I do about this?