Guitarist Walter Parks stands at the top of a natural amphitheater behind his home. On a recent weekday morning, just after a heavy night of rain had cleared, Jody Redhage Ferber lugged a cello down a grassy hill in Webster Groves. Her friend and fellow musician Walter Parks unfolded a chair for her, situating it beneath an enormous, centuries-old oak tree. And then Ferber put bow to strings. “I don’t think I can ever think of a time in my life when I’ve played this close to a babbling brook before,” she remarked after offering a solo, improvised rendition of the opening of Bach’s Suite No. 3 in C Major. “It’s like white noise — it’s strangely calming and relaxing.”