Spotify play widget (how to mute)

anybody knows the embed code to autoplay a Spotify play widget while muting it?

Same for SoundCloud if possible..

Anyone used propeller ads to get views for YouTube videos? Reviews?

Comparison to ZeroClick

out of all the methods of advertising out there..is Pop under the one that gets you the most amount of visitors per $1 ?

Or is there a more effiecent method?

Thanks