Steven Wilson's 4½ is a six-track stopgap mini album between 2015's Hand.

Cannot.

Erase.

and whatever full-length comes next.

Four tunes have origins in the previous album's sessions; another dates back to those from 2013's The Raven That Refused to Sing and Other Stories.

There is also a re-recording of "Don't Hate Me" that first appeared on Porcupine Tree's 1998 offering, Stupid Dream.

The players are by now familiar: Wilson's current working band comprises Guthrie Govan, Adam Holzman, Nick Beggs, Dave Kilminster, Craig Blundell, Marco Minnemann, Chad Wackerman, and Theo Travis.

Opener "My Book of Regrets" is a nine-plus-minute exercise that commences with a seductive pop melody, and offers a hooky chorus and syncopated dynamics.

It evolves into spiraling prog rock courtesy of Beggs' front-line Chris Squire-esque bassline, fueling Govan and Wilson's spiky (yet sharply contrasting) guitar breaks and Holzman's atmospheric synth and electric piano work.

"Happiness III" clocks in at less that five minutes and is almost a straight-up rocker with an anthemic, lushly layered backing chorus and charging guitar vamps.

Half these cuts are instrumentals.

While "Year of the Plague" comes off as a merely pleasant soundtrack-esque interlude, "Sunday Rain Sets In" starts as a Pink Floyd-ish exercise in serial atmospheres, but Holzman's post-bop piano, followed by angular, aggressive electric guitar pathos -- worthy of King Crimson -- at the close, transforms it into something more satisfying.

"Vermillioncore" is even more diverse: it moves through everything from funky jazz-rock noir to knotty, searing prog metal in just over five minutes.

The closing redo of "Don't Hate Me" -- even longer than PT's -- is denser and covers more ground musically.

Ninet Tayeb's passionate duet vocal adds cinematic drama as well as emotional resonance; a blazing Travis tenor solo (instead of the lilting flute on the original) inspires the rhythm section to fire on all cylinders.

Minimal Eastern modalism claims the center of the mix before it sets the stage for a rockist climax.

As an entry in Wilson's catalog, 4½ comes off as a fully considered EP, although leaving off "Year of the Plague" would have made it stronger.

His obsessive attention to detail is everywhere in the production, but more than that, most of this provides fans with another fantastic showcase for his amazing band, excellent writing, and fine arranging.