My iTunes library sits untouched for long stretches of time. Part of the reason is I primarily use streaming services to listen to music these days, but part of the reason is iTunes itself. I just don't like using the once-great, now-bloated application.
If you have a particular song buried in your iTunes library that you want to hear, there is a way to play it without touching iTunes. Let iTunes continue its slumber and instead turn to Spotlight search.
Open Spotlight by clicking on the magnifying-glass icon in the menu bar or by hitting Command-spacebar. Search for the song you want to play and in the results panel on the right you will see information about the song plus an album cover. Mouse over the album cover and you will see a play button. Click it to play the track.
You can close Spotlight and go about your business, and the song will continue to play. You can return to Spotlight, where your search query will remain along with a pause button if you want to stop the song. You will need to use Spotlight to stop the song because the media control keys at the top of, say, a Macbook's keyboard do not work when playing a song in Spotlight.
Also, you cannot queue up multiple songs or an album or a playlist in Spotlight but must play songs one at a time. For times when you want to listen to a song or two from your vast iTunes library, however, using Spotlight search is the quickest and easiest way to go.
For more, discover other tricks in Spotlight for OS X El Capitan.