This is extremely hard to be done slowly. You should have aged account with some music content posted way ago (if possible). Next thing is to run live streams, like at least 2 to be 24/7 (this give views to your channel) Even when you quit streaming, just do not delete that video. It will show: processing forever, stream will be removed from videos, but most of views will stay (depends on view retention) Use a single music genre like
@lynxpretend pointed, it's a must since YouTube is all about single subject promotion nowadays. Find a way to engage your audience, so you can convert them into likes, subs. That could be a giveaway for every 100th sub. When it comes to scraping music content, you will find a lot of artists who are new into your genre (use SoundCloud YT Google to seek them) They won't even ask for a credit upon uploading their work. However, always include credits, you are a legit promoter, and always use your E-mail contact at the bottom of every video for inquiries (video removal) Finally, the important part, you should create at least all high authority web 2.0 sites (including google site, blogger, academia edu), submit like 600 words articles(text spinner is not allowed, must be done manually each), low tags, and embed your videos, build channel URL backlink. Try to use proxies with different gmail accounts if possible, ex: 3 sites 1 gmail, 1 proxy, then next 3 with another. For videos, you don't need to do this with each of your videos, but try to guess what kind of content can turn viral, and pick one song of each artist you promote to do web 2.0 thing for it. You can also pay someone for articles, it is worth a lot since you will inform search engines and many other auto (bot) scrapers who will scrape your content parts and build more links for you free. Build at least 10-15 social profiles for your channel, add links to your YouTube channel, share all uploads there. Use Wikipedia to get list of all social networks.