I remember the first time I heard the music of Gustav Mahler. I was thirteen years old. It was August of the year 1967. It was a few weeks before I started high school. I turned on the radio. I heard music that grabbed my attention instantly. It was a choral work, the likes of which I had never heard before. I had to find out what the music was, who had written it. It was, of course, the Mahler Eighth Symphony, the so-called Symphony of a Thousand. I know that was the first time I had heard Mahler's music. I don't know if I had even heard of Mahler before that.
I was watching a YouTube video of the conductor Michael Tilson Thomas talking about his first exposure to Mahler's music. He too was thirteen years old the first time he heard Mahler.