[This post is by Mike LeBeau, the Tech Lead and architect behind Voice Actions. — Tim Bray]

We recently launched Voice Actions in the new Google Voice Search for Android — an awesome new way to search, control, and communicate on your phone faster than ever before, by using your voice.

One of these new Voice Actions lets users find and automatically play music. By speaking something like “listen to They Might Be Giants” into the new Voice Search, users can quickly find the music they want online and play it, using any number of different apps. (Pandora, Last.fm, Spotify, mSpot, and Rdio are among the first apps to support this.)

To do this, we leveraged a very common little piece of Android magic: a new Intent. If you develop a music app that supports open-ended music search, you can make it work with users speaking “listen to” Voice Actions simply by registering for the new intent we’ve defined. This new intent isn’t defined as a constant in the SDK yet, but we wanted to make sure music app developers had all the information needed to use it right away.

Here’s all you should need to know:

In your AndroidManifest.xml , just register one of your activities for the new intent android.media.action.MEDIA_PLAY_FROM_SEARCH : <application android:label="@string/app_name" android:icon="@drawable/icon"> <activity android:name="MusicActivity" android:label="@string/app_name"> <intent-filter> <action android:name="android.media.action.MEDIA_PLAY_FROM_SEARCH" /> <category android:name="android.intent.category.DEFAULT" /> </intent-filter> </activity> </application>

When your activity receives this intent, you can find the user’s search query inside the SearchManager.QUERY string extra: import android.app.Activity; import android.app.SearchManager; public class MusicActivity extends Activity { @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); String query = getIntent().getStringExtra(SearchManager.QUERY); // Do something with query... } } This will represent everything the user spoke after “listen to”. This is totally open-ended voice recognition, and it expects very flexible search — so, for example, the string could be the name of any artist (“they might be giants”), an album (“factory showroom”), a song (“metal detector”), or a combination of any of these (“metal detector by they might be giants”).

A few subtle details worth understanding about this intent:

Your app should do its best to quickly find and automatically play music corresponding to the user’s search query. The intention here is to get users to their desired result as fast as possible, and in this case, that means playing music quickly.

This will really only work well for music apps that can find music across a very large corpus of options. Because our voice recognition doesn’t currently support any way to provide a list of specific songs to be recognized, trying to use it against a small set of music choices will work poorly — things which are not in the set will be over-recognized, and things which are in the set may not be recognized well. So if you’re not the developer of a large-scale cloud music application, this intent is probably not for you.

We think you’ll find this new intent can greatly enhance your music app’s experience for users. And we hope you enjoy our new Voice Actions as much as we do!