I came across this interesting article about Google Play’s new Match service.  It seems that when matching your library, Google Play will substitute the edited version of a song in place of an explicit version.  Now, my guess, would be that the service simply can’t easily distinguish between edited and not edited.  It can’t really match based on TD3 tags or file names, since those are easily manipulated.  You could easily create a bunch of blank files, give them data of real songs, and then try to match them for free music.

The effective way to "match" a song in a sort of general description would be…

Google has a library of master tracks that have been hashed into some sort of searchable string of data.  Say, they convert the wave elements into a bunch of long strings of numbers.  To match, it takes each track you own, then samples a partial section of it, say, 30 seconds, then converts it using the same algorithm as it’s master tracks, then compares this result across it’s master list.

For speed it doesn’t compare the entire track.  If it has a close match, it returns the master track as the Matched file in your library.  Even a live version of a track would have a different hashed out data value, since it will have background noise such as cheering, and may have a slightly hollower "live" track.  Explicit versus censored, would likely fall within some "margin of error" however, since they would essentially be identical, minus a word here or there. 

This margin of error is necessary tot he algorithm since say, you had a track ripped from a CD with a scratch, there would possibly be a short glitch in an otherwise perfect MP3.  That sort of thing.

Basically, it’s a side effect of the scan process, not an explicit censorship by Google.

What’s kind of lame, and this has been my complain on Amazon, where I buy all of my music, for a while.  why not give me BOTH versions of the track.  If there is an explicit version available, give me the option to choose which one I want.  I have mistakenly bought the edited version of albums on Amazon before, which irritates me to no end, but I also would love to have access tot he edited music so I can let my kids listen to tracks they enjoy.

There is zero reason this is even an issue.  It would be a simple matter to link the two otherwise identical tracks on a file/license level.

Hell, even better, if the track itself could know the difference.  It’s definitely a feature that needs to be in whatever file format eventually replaces MP3 (if any).  Allow the user (or parents) to turn on the filter, and the tracks all just play the edited version automatically.  Turn off the filter, and the normal version plays, in the same file.  I hear that some BluRay discs have this option built in for movies and it would be an easy flag to build into future file formats.