If the eight songs on Black Sabbath's just-released '13' aren't enough new reunited Sabbath for you, four bonus tracks are available from a couple of different places, adding 20 minutes to the album's 53-minute running time. But how do these bonus songs stack up against the rest of '13'?

 'Methademic'

The best of the bonus tracks, 'Methademic' (from the Deluxe Edition of the album), clocks in at six minutes, putting it closer to '13''s sludgy sprawl than the other shorter extra cuts. It also packs a super-tough guitar riff by Tony Iommi, who plows through the chorus. Plus, Ozzy Osbourne checks in with a menacing chuckle around the halfway mark.

'Peace of Mind' 

Had 'Peace of Mind' made it onto '13''s final track listing, it would be the album's shortest song, coming in at a little more than three and a half minutes. But it really doesn't fit into the album's overall theme, sounding more like an Osbourne solo cut than a Black Sabbath song. Not bad, but not essential either. 'Peace of Mind' is also from the Deluxe Edition.

'Pariah'

Another leftover from the '13' sessions, 'Pariah' (found on the Deluxe Edition of the album) -- despite some lazy and clumsy rhymes -- features an awesomely thick rhythm track and a powerful vintage-style crawl that speeds into a full-on rage once it picks up some speed. Not as good as 'Methademic,' but close. And it should have been on '13.'

'Naivete in Black'

Unlike the other three bonus tracks, 'Naivete in Black' is available only on a bonus disc at Best Buy. And like 'Peace of Mind,' it has more in common with Osbourne's solo work than a Sabbath cut -- from its economical length (a little less than four minutes) to the melodic momentum that starts in the late '80s and ends somewhere in the '90s.

There's also a live version of 'Technical Ecstasy''s 'Dirty Women,' recorded in Australia this year, available on Spotify, which adds another seven minutes to '13''s total running time.