It took Planet X five years to come up with a follow-up to MoonBabies, and the first thing fans are bound to notice is the absence of guitarist Tony MacAlpine.

On this, the group's third studio album, Planet X is presented as a duo -- leader/keyboardist Derek Sherinian and drummer Virgil Donati -- rounded up by guest bassists (Jimmy Johnson and Rufus Philpot) and guitarists (mostly Brett Garsed, also fusion legend Allan Holdsworth on two tracks).

You may also find the music veering a little more into fusion territory and less into the metal-fusion genre established by the Magna Carta label -- and all for the better.

In fact, Quantum is a quantum leap above previous Planet X releases: stronger compositions (tighter and less flashy), more diversity across the album, better-dosed excitement.

The resulting music is less in your face but just as satisfying, since it welcomes repeated listens.

The fierceness presented as the band's core is its manifesto of sorts ("a band that played so fiercely, it would strike fear..." stated the press release for the group's first album), giving way to a more strategic use of intensity and better-crafted songs, as "Alien Hip Hop" brilliantly illustrates.

This album opener simply keeps on building and building over the course of its seven minutes.

"Matrix Gate" and "Space Foam" are vintage Planet X tracks -- complex time signatures, jammy feel, and a drummer that just won't quit.

On the other hand, you have moodier pieces like "Kingdom of Dreams" or the Holdsworth feature "Desert Girl," laden with jazzy stacked chords and subtler progressions.

The only piece that does not quite work out is the closing "Quantum Factor," its stop-start sections failing to form a cohesive whole; here, the band falls back to its early excesses.

That minor flaw aside, Quantum is a surprisingly mature album, the kind that could redefine Sherinian's career.

Recommended.

[Quantum was also released with bonus tracks.].