Marina Gayotos makes a living playing the bandoneon on buses and at various pick-up gigs. When she auditions for the tango master Rodolfo Mederos, he informs her that though she has talent, her bandoneon is too far gone to play. But if she can find a better bandoneon, she can play in his tango orchestra. This leads Marina to go on a quest for another instrument, one that takes her to instrument makers, dancers and an array of memorable characters from the tango world, all while searching for "the last bandoneón."
Thanks go to Steve @ Tejas Tango for the find - although I had seen a few people sharing the link on Facebook this past week as well.
Here is the link to view the full length film - 80 minutes long.
Note that apparently the film can't be viewed from within Argentina - I'm not sure about other countries.
You can also buy it on Amazon.com and possibly other sources.
The film was produced in 2005 and released in 2006.