Harmony for "Put your Records On" trio?

My two friends and are singing this at a pop concert for choir at my school and we need help! for ex. the first line one of us will sing "three little birds..window" then we all come together for "and they told me...worry" we have one harmony for the second line, but how do we find another for the other person? we tried and octave up and it sounded wierd-too strong