There are a few things you can do to grow your email list, and then use that list to grow your fanbase in general. First, it is important to research what works best for you. Different musicians have different fanbases, so the approach you take will depend on your music and what type of fan you ...
Make certain songs or part of songs, interviews, etc available until you get X amount of thumbs up on Youtube or Likes on Facebook. Gate it so they have to bring a crowd to open up the doors to new content.