On the second installation of his Immersion series, electro-acoustic composer and sound sculptor Steve Roach creates another of his sonic "zones": music for accompanied tasks or perhaps to fill the space in non-active states. This one, with "Artifact Ghost," spanning just over 73 minutes, is for the hours of darkness, preferably after midnight. Roach has been using bits and pieces of this composition for years, adding, shaping, revisiting, reconsidering it until he created the final map for the project and recorded it in its entirety. He used an excerpt on Texture Maps (eight minutes from the original 90, making this recorded version an edited one), and as the introductory music in his tours in the '90s. This is not so much an electronic tone poem, or dronescape, so much as a carefully -- perhaps even painstakingly -- constructed meditative piece that contains subtly shifting textures, dynamics, and even tensions. This isn't music to fall asleep to, this is music to listen to while one is dreaming, especially while one is in a state of active dreaming. Here, the synths and spaces line up, shape something from the ether and evolve, continuing on their way to evoke images in the mind of the listener, perhaps even heart images, where there is evident a kind of openness and exhortation of bravery to look deeper and see these shapes for what they are. "Artifact Ghost" is always moving, there is no real stillness, even in the considerable number of pockets or spaces, as cave and water sounds drip, slip, and commingle. It's a piece to be returned to over and again much as the Dream Circle from 1999 is, but it contains little of the stasis or purposeful blessed-out texturalization. This is an ever-inner space, where what came before is invited into the moment, into a present that may last minutes, hours, or days depending on the listener's intention. And it is that intention that makes Roach so different from his peers. The listener is an active participant -- yes, even while sleeping -- in the way the music exposes itself as subjective image, memory, and perhaps even prophecy. The Immersion series is Roach with all of his craftiness at work. It is one of the most creatively provocative and aesthetically necessary projects he has undertaken in his long and prolific career. This is the definition, subjectively at least, of what ambient music is and is for.