To take advantage of this new feature, all you have to do is type in the name of a song; this sometimes is not enough if the song title is a common word or set of words; in this case, add the name of the artist.
For example, let's say you want to hear the song Ironic by Alanis Morissette.
First, go to Google. Since the name of the song is a dictionary word, the title by itself will not be treated as a song: You need to include the name of the artist as well.
Search for "Alanis Morissette - Ironic". (For the truly lazy, this link will do the search for you)
But after the first play of the song, you only get 30-second previews after that. iLike, Google's partner in this music search has this to say:
How come when I play music from Google search it doesn't always play the full song?
For most songs, the first time you play the song, it will play in full, but if you play the same song again, it will subsequently play it as a 0:30 second sample clip. If you want to hear the full song many times, we encourage you to purchase the MP3 using the convenient "Buy" link.
For some songs, due to our contracts with record labels, we can only play them as 0:30 second clips for now.
Well, now you have it. But there is a way around this: Use imeem! If you see a little iMeem link available, you can hear the full-length song as many times as you want - the only catch is that you need a (free) imeem account.