TikTok, Instagram, and YouTube Shorts, you can find some nice songs to add to your playlists. And to make this process easier, YouTube now offers a new integration between its short videos and its Music app, which lets you add songs to a YouTube Music playlist without leaving the YouTube app, when you watch a YouTube Short video and like the song that the creator has used, you can tap on the square music album art button at the bottom right corner of the app. This will open a new page, which will show you all the short videos that currently use this song. Just below the name of the artist performing the song, there is now a new bookmark button named "Save." When you tap on it, YouTube will automatically add this song to a new playlist in the YouTube Music app called "Sounds from Shorts." And there, you will see the newly added song. So now, every song used in a short you save will go to this playlist. However, if you save a short that doesn't use a real song, it won't be saved to the playlist in the Music app. We should also note that the system will create a Sounds from Shorts playlist in the YouTube app as well. But here, you will find every short you have saved, even if someone just talks in the video and doesn't use a song. 

It appears that the new save feature comes from a server-side update and is on a slow rollout, so you may need to wait for YouTube to release it for you as well.