Read this:
"YouTubers do not need to ask permission when reusing music found here in their videos, the above system is for YouTube Partners that wish to make use of it. "
This is on all of his newer stuff. He says it could be a couple of days or a couple of weeks to get a hold of the artists IF they choose to respond. My history with contacting an artist (before this new system) has been pretty positive, though.
For those who want to use these tracks on monetized videos, you need written permission. Check the older uploads, though, they have the written proof linked in the description. OR, you can request written proof from the artists, but that may take time and not work out well if you need to upload soon.