"Summertime"

I recently listened to Gershwin's Porgy & Bess performed by the Bethlehem Orchestra.  In that version of "Summertime," "wings" in the line "Then you're gonna spread your wings and take to the sky" is sung with a melisma, lending a sense of this "spread[ing]."  While this articulation isn't present in the Zombies' version, I realized that there's an-other musical feature that provides a similar effect:  after "spread your wings," the bass plays a group of notes that span a sixth (A D E F).