Complex sentence: Both brothers were introduced to a wide variety of instruments, and became multi-instrumentalists, with both being taught to play the piano, with Oteil gaining proficiency on the bass clarinet, violin, and trumpet.
Split into simpler sentences: Both brothers were introduced to a wide variety of instruments, and became multi-instrumentalists, with both being taught to play the piano. While Oteil gained proficiency on the bass clarinet, violin, and trumpet.