There is every other kind of improvised music under the sun, and then there are The Necks. Since 1987, the Australian bass-drums-keyboard (and, occasionally, bass-drums-keyboard-guitar) trio has been doing one thing superbly, ecstatically and consistently well: performing spontaneously improvised sets of music of a more or less regular length. The longtime 60-minute men have sometimes dialed down that duration in recent years, though. So their typically spellbinding 17th studio album, Travel (North consists of four examples of the 20-minute improvisations that typically begin a Necks day in the studio. Expect jaunty eloquence (“Signal”), emergent spirituality (“Forming”), deep meditation (“Imprinting”) and vital recirculation (“Bloodstream”).