Answer:
Good music system and unique music.
Step-by-step explanation:
Good music system and unique music makes a concert rock because in the concert the main thing is music. if music is not good either due to bad music system or bad music performed by singers, the people show no interest and they leave the concert. The people participate in the concert in order to hear good music so by making a concert good, they have to provide good music system and also good music.