Sebastian in the percussion section makes <<1=1>>1 person.
The brass section has 4 + 2 + 1 = <<4+2+1=7>>7 people.
The strings section has 3 + 1 + 1 = <<3+1+1=5>>5 people.
The woodwinds section has 3 + 4 = <<3+4=7>>7 people.
The maestro is 1 person.
Thus, the orchestra has 1 + 7 + 5 + 7 + 1 = <<1+7+5+7+1=21>>21 people in it.
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