We're Off to See the Wizard - S4-E19
Visible crew/equipment: After Phoebe tells Cole she's pregnant she leaves in the elevator, and when it cuts to Piper, Paige, and Leo we can see the crew's grey mat on the floor under Piper and Paige, then in two following shots (from the same angle) the red T-mark is visible on that mat, at Paige's feet. (00:07:45)
Answer: "Hush, Hush, Hush" Paula Cole.