Initially, the sound of Juliek's voice reminds Eliezer of the past, of orchestras and music and concerts prior to the concentration camps. The realization that Juliek still had his violin with him seemed too unlikely to even be given much consideration.
When Eliezer heard music and realized it was not a dream but Juliek actually playing the violin that had also survived to that point, Eliezer recognized that he was hearing Juliek's dying statement. For Juliek the musician, his life did not flash before his eyes as visions in the moments prior to his death. Instead, his life played out its review in his music.
His whole being was gliding over the strings. His unfulfilled hopes. His charred past, his extinguished future. He played that which he would never play again.
Eliezer understood that Juliek was paying tribute and saying goodbye in the way that he knew best.