Which individual was the assistant band director from 2015 to 2017?

The correct choice is that Mr. O'Neil Sanford served as the assistant band director from 2015 to 2017. This timeframe coincides with his contributions to the JSU Band program, where he played a crucial role in shaping the band’s performances and educational experiences during those years. His commitment to the band and his impact on its members are essential elements of this period in the school's band history.

While Mr. Kevin Johnson, Mr. Chan Leggette, and Dr. Ramon Jackson have all played significant roles within the band program at different times, their positions and tenures do not correlate with the specific timeframe of 2015 to 2017 as outlined in the question. Understanding the unique contributions of each individual can provide context on their significance in the overall history of the JSU Band, but Mr. O'Neil Sanford's specific role during those years makes him the correct answer.