If you're looking to turn a song into your phone's ringtone, you have a few options. You can download the music from any song portal or as an MP3 audio file. After downloading the music, you can crop it to create a ringtone for your phone. Unfortunately, YouTube doesn't officially offer a way to download a video in audio format.
However, there are some solutions that allow you to download the music or ringtone of your choice from a YouTube video. This can be especially useful if you can't find the ringtone on popular ringtone portals or other websites, or if the song you're looking for isn't available on other streaming platforms for download. Keep in mind that these audio tracks cannot be downloaded as native music files for offline listening or settings such as a ringtone on a smartphone. However, there are solutions that allow you to download videos and music from multiple sites in addition to YouTube and convert them into ringtones.
Once you've downloaded the song, you can use it as a custom ringtone. On your iPhone, select the Standard Ringtone option and this will set the song clip as a custom ringtone on the iPhone. You can also assign the song to a contact or add the custom ringtone to the list of other ringtones on your device.