Pianist Peter Kater has orchestrated a gentle, introspective series of ambient chamber works dedicated to the four elements: Earth, Water, Fire, and Air. Each CD is distinctive, with Water living up to its title by being the most free-flowing of them all. Using long, pensive pauses and melodies that elongate over time, the music borders on classical — often echoing classical themes, such as the Satie-like ostinato of “Water Ballet,” without overtly lifting from them. Water comes close to the painfully serene sound you might associate with Arvo Pärt. Accompanied just by guitarist Mike Hamilton and reed player Paul McCandless, they explore pensive chamber moods, many of them built around improvisations I suspect Kater pieced together into compositions later. Conceptual albums like this are often as much about marketing as music, but on Water, Kater’s compositions genuinely do seem to float in slow tide changes and gentle pools. He stays just to the right side of sentimentality and, at times, reaches the sublime.