After weeks of, Apple finally yesterday. For $24.99 a year, iTunes Match grants you access to a copy of your iTunes library stored in the cloud. Subscribing to and setting up iTunes Match is a snap; all you need is patience commensurate with the size of your iTunes library.
First, make sure you are running the latest version of iTunes. On a Mac, go to iTunes > About iTunes to see which version you are running. If it's not version 10.5.1, go to iTunes > Check for Updates to download and install the latest version. On a PC, you can access the About iTunes and Check for Updates menu options from the Help menu.
After upgrading to iTunes 10.5.1, you'll see iTunes Match listed under Store in the left panel. Click on it and then click the blue "Subscribe for $24.99" button. iTunes then starts scanning your library before trying to match your songs with its huge library of songs in the cloud. It then uploads the songs (and artwork) it was unable to match. Of the 6,885 songs my library, iTunes was unable to match 1,380 songs. Of course, mileage may vary.
Once you have gone through this matching process, you can now access these matched or uploaded songs in the cloud from another computer with iTunes or from an iOS device. Apple lets you share iTunes Match with up to 10 computers and iOS devices.
Adding an iOS device
To connect an iOS device, go to Settings > Music and you should see a new menu item at the top: iTunes Match. Switch the slider to On, enter your Apple ID password, and then hit Enable. Note that iTunes Match replaces the music library on your iPhone, iPad, or iPod Touch. This shouldn't be a problem if you sync your iOS device with iTunes because it won't contain any songs not already found in your iTunes library.
After enabling iTunes Match, a new menu item gets added to the Settings > Music screen: Show All Music. With Show All Music on, all the songs matched or uploaded from your library to the cloud will be shown in the Music app. If it's off, then you'll see only those songs you've downloaded. iTunes Match doesn't stream music to an iOS device, but downloads a song when you choose to play it. (You are able to listen to the song as it downloads.)
With Show All Music on, you'll see your entire iTunes library in the Music app. Each album or artist stored in the cloud will have a cloud icon next to it. And when viewing songs, each song will have a cloud-with-an-arrow icon. You can simply tap a song to begin playing and downloading it, or you can tap the cloud-with-an-arrow icon to queue up a number of songs to download.
Adding a computer
To access iTunes Match from another computer, first check that it is running iTunes 10.5.1. Then sign in to your Apple account and click on iTunes Match from the left-hand column. Instead of asking you to subscribe to iTunes Match, Apple asks if you'd like to Add This Computer. Click on the button to add the computer and iTunes will run through the three-step process of scanning, matching, and uploading your library. Only one iTunes library can be matched at one time, so let your first library finish before adding a second.
After going through the setup process on a second computer, you'll have access to all of the songs you have already matched from your first computer. And your other computers and iOS devices on which you have enabled iTunes Match will have access to the songs from this library.
In iTunes, you'll see the cloud-with-an-arrow icon next to all the songs in the cloud, which you can click to download that song. Unlike with an iOS device, however, you can play a song from the cloud in iTunes without downloading it.
That's it. The only hassle is waiting for iTunes to upload songs for which it can't find matches. And I was surprised that songs from well-known, mainstream artists such as The Roots and The White Stripes weren't matched. I suppose iTunes Match is a work in progress. Even in it's early stage, however, it's an inexpensive and useful service for accessing your iTunes library from additional devices.