YouTube unfortunately does not provide you with the ability to upload audio tracks individually, which is a pain if you do not work with video (such as a podcast).
The way to get around this limitation is to create a video which includes the desired audio track and a fixed image (i.e. cover-art) which lasts the duration of the track.
There are many ways of achieving such a result, from iMovie and Windows Movie Maker to the online service TunesToTube.
With a little research however, I was able to come up with a even simpler solution that only requires the ever useful ffmpeg.