The Dutch pianist’s jazz credentials include a celebrated recording with Eric Dolphy and all-star tributes to Herbie Nichols and (again) Monk. But Misha Mengelberg is also a lifelong student of new music, with a penchant for spontaneous mischief-making. Impromptus, a long, arresting recital, consists of 13 ”Impromptus,” in which he plays piano (the keys and the innards), sings (on ”6” he sounds like a bebop chicken; on ”#8,” the entire cast of a ”Punch and Judy” show), and whistles. He’s funny, touching, and surprising. FMP is now the leading free jazz label; the catalog can be ordered from Free Music Production, Lubecker Strasse 19, 1000 Berlin 21 (West). B+