Please answer the following question: Generate a question about the following movie plot: A group of school girls in northern Japan are stuck in class for the summer, where they find nothing interesting. One girl Tomoko encourages her classmate to deliver the lunches for the school brass band cheering for their school baseball team, thereby getting out of the class for a day. Tomoko and her friends realize helping Takuos plan to fight the next big game could get an opportunity for them to skip the math class all summer. Takuo not having enough members to form a brass band decides to make the girls into a big band swing group. Tomoko buys a saxophone and starts to learn on her own. With the help of Takuo, she makes the other girls involved. They start to practice and slowly learn how to play. The Swing Girls are born
A:
What instrument does Tomoko buy and start to learn on her own?