bandoneon
A small Latin American accordion played with buttons which is frequently used in tango ensembles.
Piazzolla studied piano in New York with Rachmaninoff and went to France to study with Nadia Boulanger, but his first and favorite instrument was the bandoneon, an accordion-like instrument invented in 1854 by Heinrich Band that has a series of buttons instead of piano keys.
Where it comes from
From Spanish bandoneón, from German Bandoneon, named after Heinrich Band.
Adapted from the Wiktionary entry bandoneon (CC BY-SA 4.0).