In 2013, a very cool initiative was taken by the SNCF train company: a piano was installed in the public area where the travellers wait, and it’s accessible to whoever wants to practice. (They’re in Paris train stations, but also in other French stations, and I also saw one in Amsterdam during the 2014 Spotters weekend!)
Since I sometimes go across the station Saint-Lazare it’s a real pleasure, when I have to wait for my next train, to stay around the piano listening to the improv artists. Especially late in the evening, when the station is nearly empty, and most people around are lonely or tired, but want to find better vibes to finish the day through these piano sessions …
I also like the fact that there’s no specific rule for those who want to play, no list, no queue, but a general agreement between the piano players, and sometimes singers too who ask the pianists to play their favourite songs.
Every major train station in Paris has its own “À vous de jouer” piano (it literally means: it’s your turn to play): Saint-Lazare, Montparnasse, Austerlitz, Gare de Lyon, Gare du Nord and Gare de l’Est. The pianos are usually located near the Transilien (suburban train network) platforms (upper levels), and not at the metro or RER underground levels.
So, if you miss a piano to practice on while travelling in Paris, or if you simply want to share a warm spontaneous atmosphere, look for a train station!