Playing now in the Buenos Aires Metro are members of the Opera Periferica enemble, rehearsing their upcoming production of Pergolesi’s La Serva Padrona.
It’s on the H line, if you happen to be travelling in BA.
Next year, they plan to perform in the Madrid Metro.
I was in Madrid about 3 years and went to the opera for a rather routine Barber of Seville (the dancing was authentic!). Walking to my hotel through a pedestrianized area I came across 4 musicians playing the slow movement of the Bach double violin concerto, surrounded by a totally silent crowd. Memorable and magical.