Snaptube
Snaptube is an Android app which allows you to download mp3 songs right from Youtube. Snaptube also supports other major video/audio websites like Dailymotion, Vimeo, Twitch, Tiktok & others.
With Snaptube on your Android phone, you can surf the web and visit any website. Download button will appear as soon as any media file is detected such as Videos and Music.
If you are an Android user, you can download Snaptube apk from their website for free. As downloading from Youtube is against their TOS, Snaptube is not available in Play Store.
As for iOS users, unfortunately Snaptube is exclusively only on Android.