Focusing on the threatened demise of a musical instrument, Jiska Riskel’s glorious musical treat is both a moving odyssey through Argentina’s musical past and present, and the search for the soul of the bandoneón. Just as the inventors of the harmonica and the melodica could have had no idea that their innocent instruments would one day transform blues and reggae music, the German immigrants who brought their “poor people’s organ” with them to Argentina in the 19th century probably didn’t anticipate the rise of the tango. But the bandoneón’s astringent, sliding tones suggest passion like no instrument before or since; the tango, this film implies, was built around that sound. Between 1911 and 1943, 60,000 were sold. But unlike guitars and glockenspiels, no one’s making bandoneóns any more, a lot have been bought up as souvenirs and the few left are in need of constant repair. Rickels, like a musical David Attenborough, hunts down this vanishing species in its natural state, revealing the hands of great bandoneónistas like Nestor Marconi, seen playing in fabulously preserved old dance halls, and Daniel Vedia, teaching poor students in the countryside. Despite its melancholy subject matter, the film’s air of slightly bitter nostalgia and fantastic musical selections make it as bracing as a great tango.