How to promote more music singer?

There are thousands of services online that can be of help to a person marketing their music online, however, whether online promotion makes a difference at this stage, depends on the actual product (artist / songs, etc) that you are trying to promote. What you should be doing at this point, if you have not already done so, is collect feedback from music business professionals such as musician managers, music bloggers and reviewers, Radio & Club DJ's, etc, who are able to give you some real valuable feedback on what stage of development your singer and the product is at today. But more importantly, your 3 Million YouTube views should have translated into a significant number of "fans" who paid to download your music. This video should have translated into some significant buzz online. If it did not, then yes it's obvious you need to rewire your current online marketing approach. Without having seen your video, It's difficult to further advice on the appropriate next step. Just know that getting to the top of iTunes, or anywhere else can be easily paid for if you have the budget. That's how the big boys/girls still do it, and as you know, it's not always all about talent.

Hi Maksym, sorry for the delay.

If you are really serious and have a large budget, you can play the game most independent artists don't want to play because it involves paid ads etc.

Look into the following.

Apple - Advertising

Through them you can have your music heard on this...

Apple - Advertising - Experience - iTunes Radio

and seen on this...

Apple - Advertising - Experience

As mentioned, there are many other ways to pay for promotion online, however I am sensing that your focus is on getting traffic to your iTunes artist, so try to target your potential fans (genre etc, and zoom in on people who are already actively buying iTunes.