MacBook Pro (13-inch, 2018, Four Thunderbolt 3 Ports)
macOS Mojave 10.14.3 (18D109) (latest)
Spotify 126.96.36.1998.g9064793a (no newer update available)
While playing music the audio system daemon "coreaudiod" uses between 8% and 11% CPU which seems to be normal for macOS. But I have now noticed that it uses between 25% and 29% CPU as soon as I pause the music. This seems like a bug because one would think not playing sound is less intensive than playing sound. This problem has persisted after restarts of Spotify and my computer. Quitting Spotify makes the problem go away, coreaudiod goes idle and uses it pretty much 0% if nothing else is playing.
The usage does back down to the normal amount if another application is playing sound while Spotify is paused. This confirms that this is Spotify's problem and not a bug in coreaudiod. When other applications are paused, coreaudiod simply goes idle as it should.