Watching videos on YouTube is a really great way to keep yourself entertained or discover new things, so it is understandable why it is the most popular media-sharing service in the world. However, there are those of us who use it only for background music at work or focus on other activities, so the fact that it doesn't offer a music-only feature is a bit inconvenient. I know what you're going to say: use YouTube Music Key, but no one offered me a free subscription to that service (yet). This is why installing a tool like Streamus can really pay off.
Streamus is a neat Chrome Extension that helps you transform YouTube into an ad-free music streaming service. Simply put, this add-on lets you create your own playlists (as many as you want) from YouTube videos and then plays only the audio stream, so your computer won't be consuming memory for videos constantly running in the background. What's really cool is that you also have a radio service which works pretty much the same way Pandora does. The feature takes into account the songs in your current playlists, and it automatically adds new ones when there are no more tunes to play in your current queue. Streamus is completely free and can be downloaded from this link.
Unfortunately, at the moment, there seems to be a bit of a problem with the extension as it is unable to connect to YouTube. According to the developer (who was very prompt in acknowledging, explaining and fixing the issue), YouTube has recently changed its code to fix a bug, which indirectly affected Streamus's programming as well. Even though an updated (fixed) version of the app already exists (here - it requires a bit of effort), it is not yet on the Chrome Store. Apparently, Streamus registered such a sudden growth in users that Google's Chrome Web Store automatically red-flagged it, and it now has to be manually verified by the staff before any updates can be made.