The only musician we learn anything about in Night by Elie Wiesel is a Polish man named Juliek,
a Pole with eyeglasses and a cynical smile in a pale face.
Elie meets him in Buna when he and his father are sent to stay in the musician's block at the Buna camp. Here we learn, from Juliek, that while the Germans allow the musicians to play, he has forbidden them to play music written by any German composers. Of course we understand that is because Hitler considered all Jewish people to be "dogs" who would only contaminate his country's great music--a ridiculous notion, as we all know.
Juliek is transferred to Buchenwald along with many others, including Elie and his father. The march is brutal, as it is winter and they prisoners are given virtually nothing to eat and and have no real time to rest. It is a terrible ordeal, and Elie kind of keeps track of his friend Juliek.
When they arrive at the Gleiwitz barracks, a stopover on their journey to Buchenwald, the survivors of the march are nearly done in and they all fall asleep on top of one another. Unfortunately, this is dangerous because there was a danger of being smothered in the crush.
Elie wakes up that morning and hears a haunting, unfamiliar sound. Once he identifies the sound, he is stunned at what he hears.
A violin in a dark barrack where the dead were piled on top of the living? Who was this madman who played the violin here, at the edge of his own grave? Or was it a hallucination? It had to be Juliek. He was playing a fragment of a Beethoven concerto. Never before had I heard such a beautiful sound. In such silence.
Your question asked where the music was played, and this is where: the dark, stifling, unfamiliar barracks of Gleiwitz.
Juliek is playing the violin as if it were his soul, and the music is moving. It is as if those dirty, starving, and defeated prisoners knew Juliek's life and heart as they listened to his music. He is playing a selection written by Beethoven, and it is a beautiful and sacred moment.
For more interesting insights and analysis of Night, be sure to check out the excellent eNotes sites attached below.