While the novel coronavirus has wreaked havoc on the music world, a few musicians have caught the bug and recovered. I didn’t even know folk icon Tom Rush had the disease until he announced this week that he has beaten it — no mean feat for a 79-year-old. He’s always been known as much for covering both old folk tunes and championing then-unknown singer-songwriters like Joni Mitchell and James Taylor as for his own material. This is arguably his best-known composition.