Yes it is possible to play no video on YouTube only audio
You can easily load YouTube videos with audio-only content using Audio🔊 only on YouTube™. On/Off switches are provided by toolbar buttons. The add-on is active when the button's colour is red, and it is inactive when the button's colour is lite grey. Please be aware that the default state is on. The addon automatically loads the audio source only and stops the video content from loading when you open a YouTube page and play a video. Due to the fact that the video content is much larger than the audio content, you will be able to conserve internet bandwidth in this way. Additionally, there is no need to load the video content at all if all you want to do is listen to the video.
▶ YouTube can be switched to audio only with a single click.
▶ only applies to HTML5 video elements (flash is not supported).
▶ includes a background image as a placeholder for the video elements.
▶ Available across all operating systems for the browsers.
▶Very lite and easy to use Extension.