This is admittedly an old-ish feature — apparently it’s been around for over a year — but I had no idea it existed. Spotify Connect lets you play your music on any of your devices, and control it from any other device. The way it works is really simple: from any device you’re using to interact with the app, you get to choose which one of your other devices will actually play your music.

And it does work, like a charm. As a matter of fact, I’m using it right now to play the new Thelonious Monk collection between my iMac and my iPad. The iMac controls playback and the iPad, which is plugged into my home’s HiFi sound system, plays the music. And unlike AirPlay, I can still play all kinds of other sounds locally on my iMac.

That by itself is pretty cool, but the best part is that I found out about it completely by chance — or, rather, by clever design. Spotify allows you to play your music on only one device at a time, and I was already playing music on my iMac. When I launched the Spotify app on my iPad to switch devices, I was greeted by a dialog offering me to continue playing the iMac’s music. I just touched yes and my music immediately started playing on the iPad, right from where the iMac left off. No lag, no buffering delay, nothing. It really couldn’t have been any simpler.

This is what great software design is all about. New features should not only be easy to use, they should be easy to discover. In this case, I did everything in my power not to discover Spotify Connect — by not reading anything about the app and not playing around with the interface after every update — and the feature still ended up making itself known to me. That’s great design, and it is awesome.

It has also saved me quite a bit of money, by the way. For the past few weeks I’d been this close to buying an AirPort Express just so that I could stream music from my iMac to my stereo, but now I don’t think I’ll be needing it.