Something that comes to mind reading @Boydie's comments above:
Another avenue is the ease of social network "sharing"
Say I perfrom a vocal for another artist. They can post it on THEIR youtube/soundcloud account. I can then
-share the posts on my Facebook/twitter with notes about my work on it.
-repost on soundcloud to my followers
-Share on google+/YouTube channel
All of the above benefit BOTH parties. The writer gets the hits from a whole seperate fanbase, and the vocalist gets some self promo out of it.
I have seen this happen a LOT and it is a great way for the little guys (i.e. EVERYONE on this website
) to build momentum.
This way, the artist isn't using the work directly on their channels, but it IS being seen by their fans.
This type of thing negates the secret squirrel issue while retaining control. It is what I would do if I had people work on my songs