How to sync MP3s to Spotify (photos)

Spotify's music subscription service is a great way to discover and share music, and with its mobile app and a Premium account, you can take its huge library of songs with you anywhere.
But every once in a while you'll encounter a track that isn't on Spotify, but you know you have it in your personal collection. On a Spotify Playlist like the one shown here, you'll see these tracks as grayed out and unplayable.
The situation isn't hopeless. With a little extra work, you can meld your music collection into the Spotify app, and leave the iPhone's stock music app behind.
To see a video version of this tutorial, head over to CNET How To.

For the first step, open up the Spotify app on your computer and check to see that you have a Premium account by going up to your name and clicking Account. You'll see your account status here. If you don't have a Premium account and you really want this feature, now's the time to upgrade.

Next, head over to your Local Files listing in Spotify. This is going to show you all of the files on your computer that you can sync over to the Spotify app.
There's a total at the top, and if it seems off, go into the Preferences menu and make sure the folder where you keep your music is included in the local files checklist. Because I had my iTunes music folder in a location other than the default, I had to add it to Spotify manually.

Now, to avoid the hassles of supporting Apple's proprietary USB dock connection, Spotify opts to sync with your iPhone or iPod Touch over Wi-Fi.
To make this happen, check to see that both your iPhone and your computer are connected to the same Wi-Fi network. Open the Spotify app on your phone, and you should see it pop up under the devices listing on the left side of your computer's Spotify app. Click the icon for your device and you should see this prompt to start the syncing process.

From this view you can tell Spotify to transfer your entire music collection or individually select which playlists to sync over. Spotify will now sync your files over Wi-Fi and you'll see a running tally of how much space is available on your iPhone at the top. Once transferred, you'll see your tracks pop up under the Local Files listing on your phone.

Here's what an in-progress sync looks like from the view of the Spotify desktop app (notice the green progress bar on the left).

And here is the same in-progress music sync from the view of the Spotify mobile app.
For more tips like these and a video version of this same tutorial, head over to CNET How To.