I have heard from an unreliable source that it is best to shoot your music video at a faster pace and slow it down in post. I know that was true when they shot on 16mm but is there any reason for it in digital format? I am shooting on the HVX and I am wondering what the best frame rate is for a music video.

it is all a matter of what look you are going for. if you overcrank the camera you will get a kind of dreamlike quality... it is important that you remember to speed up the music in proportion to the speed you overcrank the camera...with the hvx you can get 26 fps which would only make the effect slight, and more prominent at 30....if you shot at 36fps, you would have to play the music at 1.5x the speed since you are recording 1.5x the number of frames that you will watch it at.....but you by no means have to do this. it is a choice you have to make depending on how you want the video to look.