Both YouTube and website use, where there is no charge to access the content, falls under a regular standard music license.
It sounds like these videos can be considered part of a “series”, and you will need only the one standard music license - subject to the relevant terms.
Here’s the text of the relevant terms, taken from the License FAQ
Do I need a separate license each time I use an item in a series?
No. You only need to purchase the item once per series.
What constitutes a series (eg TV series, webisodes, or a magazine with monthly editions)?
To be considered a series, all things in the series (eg episode, edition) must be connected, and be released within 1 year of the first installment. There is also a maximum of 52 episodes or editions within the series.
Example: A 12 episode TV series that starts in December and ends in July would only require a single license. A YouTube series that releases an episode every week (52 total) would only need to purchase a license once every year. A magazine that releases an edition every other month would need to purchase a license once every year.