Online music marketing comes in all forms. The most common practice from what I can see is social networking sites. Social networking sites are great places to market your music but it will be to your benefit to dig even deeper.
To really boost your online music marketing campaign you need to become active on music forums. You may use forums and I'm sure you have at least heard of them but there are certain ways to interact on forums to really maximize your results. You can also look for online music marketing courses.
It is important to get involved with forums that will give you the opportunity to promote your music to a targeted audience. For instance, if you play grunge rock try to find grunge rock forums and if you play punk rock, find punk rock forums.
The idea is to find the exact sub-genre of the main genre you are in. This will get your name out there to a very targeted audience. You may be promoting to a smaller group of people but your online music marketing campaign will improve.
Get involved with about three different forums and post on them regularly. It's really important to conduct yourself properly on these forums so that you are received with open arms.
Online music marketing success can be achieved in forums when you use them correctly. Find the forums that target your genre and sub-genre and most importantly make sure you conduct yourself with integrity.