Just an idea regarding the instagram thing. Why don't you just get permission from each artist for each post via a comment on their post? I think followers on instagram will understand that Sonic Groove Live is not all these people, and explicitly state that the content was used with permission in the Instagram post.
Then provide a @ tag for the artist and to visit steemit to check them out.
If the person does not give their permission, then don't use it. The coverage may be incomplete because of this but it will still be a great marketing tool for Sonic Groove Live and for Steemit.