On Bajo Cero (Khaeon), the tango nuevo accounts from pianist Pablo Ziegler, guitarist Enrique “Quique” Sinesi and bandoneon player Walter Castro are prominently attractive. Ziegler, who was Astor Piazzolla’s pianist for 11 years, is a performer of considerable note. Aping or merely honoring the tango master, however, is not his agenda; improvising the tango is. Ziegler is irrevocably committed to improvisational paths of his own, albeit tipping the hat to Piazzolla by reinterpreting two of his compositions. Fully engaged in “Chin Chin,” for example, syncopated chord melody resolutions, interactions and challenges are tossed at will. On the band’s open and breathy “Milonga del Adios,” nonetheless, their collective musical determination caresses the harmonic sequences that lie close to the heart of jazz standard fare, tango and its cognates. It’s wholly uncommon to find a trio with this much cojonudo moodiness, dramatic personhood, virtuosi chord conception and masterful technique.