Youtube content creators get paid via a few different methods:

1. Pre-roll and mid-roll ads. This is youtube's actual and intended monetization method. These are ads that play that are separate from the video and are personalized per-user. They often have a "skip" button you can click after a few seconds. Youtube pays creators per view for these ads. You should check youtube's monetization section on the channel settings to set this all up.

2. Sponsors. These are baked into the video where the content creator usually goes something like "Yeah I enjoy my switch, but do you know what I like more? raid shadow legends!" These are one-time payments made prior to the video's release, and are not paid per view. The view count on the video and whether or not people are actually watching the sponsored section is irrelevant.

3. Patreon and other patreon-like services. These are entirely unrelated to viewcount or ads, and are just people paying monthly on some other site (typically patreon or locals) to help fund the channel.

For music, I'm not sure at all how the youtube music platform works. But afaik youtube music is just youtube videos in a different format, so you'd be going with method #1 with the pre-roll ads.

Typically youtube's monetization model requires that you actually set things up, and in order to do so you need to meet particular criteria (particular subscriber counts, view counts, etc). I know musicians work with music labels, so that may work differently depending on what's going on for you. But if you're specifically managing a youtube channel where you upload videos, then #1 applies and just check the monetization section. I don't think it's "by default".