The term "original music" generally means musical works written by the performing musicians. That doesn't mean, however, that the musicians are not affiliated with BMI. This is because licensing organizations like BMI are the vehicles through which songwriters and composers are compensated for the public performances of their music. In addition, one of the purposes of BMI is to help foster the development of up-and-coming songwriters, many of whom perform in public areas such as yours. Many times, these performers are asked to play songs known by the general public that was written by someone else to add to the entertainment. These performances also require permission.