Power comes from Rotation! Just like walking, we set an Anchor, then we Vault our body past the Anchor, Rotate on to the other side, then release the Anchor and repeat. This should make freestyle a light, Rhythmic stroke.
The arms are an extension of The Line first, and tools for Balance second. Emphasize the Transfer of Energy by Throwing the weight of the recovering arm forward from the shoulder to the elbow in a circular motion in front of the bodyline, beginning about halfway through the recovery phase. The hand is not very important and should remain relaxed. The elbow does not have to be high and bent, it is more important that the energy is thrown from the shoulder to the elbow in a circular motion in front of the bodyline. When you feel the stretch along your Throwing side it is time to Vault your body past the Anchor set by your opposite arm, and to Rotate to the other side.
We want Curvilinear movements for the Transfer of Energy, not straight ones. Curvilinear movements are more efficient for transferring energy, and do not lead to shoulder injuries!
Note: This is not catch-up! Catch-up is a Low Side dominant stroke with emphasis on pulling under the water. We want a High Side dominant stroke with emphasis on the Transfer of Energy above the water. It is easier to transfer energy through the air than through the water.
Remember: A high elbow, straight through recovery leads to shoulder injuries! Keep the elbow in front of the body line, and swim on your side with the hand relaxed.