When the Philadelphia Orchestra paused live performances in March, violinist Booker Rowe didn’t expect it would be his final curtain call. Rowe, the first African American to play with the orchestra, retired in August after more than 50 years. He and his wife Dr. Patsy Baxter Rowe, a singer and musical scholar, discuss why his historic career illustrates that progress can be made to diversify the traditionally white world of classical music — and why that world still has a long way to go.