Google has given YouTube Music a leg up by making an ad-supported version free on all Google Home speakers. It rather seems like Google is trying to make YouTube Music its default music service despite the wide-support for Google Play Music.
In fact, the same free service is available on any Google Assistant-powered speaker, not just Google Home. The service is limited to general themed-based stations ("Hey Google, play rock") rather than specific requests.
Naturally, you can upgrade to YouTube Music Premium for $9.99/£9.99 a month so you can request specific albums, songs, artists, and playlists on-demand.
YouTube Music Premium also enables you to play background music through the YouTube Music app while using other apps and also enables you to download music for offline listening. And, of course, it's ad-free.
To set YouTube Music as the default on Google Home, navigate to Account Settings in your Google Home app, tap Services and select Music. Then, select YouTube Music as the default music service. With new devices, you can select YouTube Music during the setup process.
As well as the US and the UK and Ireland, the service is also available in Canada, Mexico, Australia, Ireland, Germany, France, Italy, Spain, Sweden, Norway, Denmark, Japan, Netherlands, and Austria. It’ll be available in more countries soon.