Named after the English castle where Mary, Queen of Scots was beheaded for treason in 1587, Fotheringay — founded by ex-Fairport Convention singer Sandy Denny and singer-guitarist Trevor Lucas, from the highly regarded band Eclection — were the closest thing British electric folk had to a supergroup in 1970. They were not super enough to make it through 1971, breaking up in the first week of that year when Denny decided to go solo, leaving their second album half-done, as basic tracks and guide vocals. Even in that state, 2 (Fledg’ling) — a reconstruction of the intended record, produced from original master tapes by the band’s guitarist, Jerry Donahue — is a gently momentous shock, lacking final studio polish but capturing with compelling understatement the group’s brief success, fusing homegrown antiquity with the more contemporary twang and drawl of pre-Nashville-factory country and the Band’s prairie-story rock. The 1970 debut, Fotheringay, had a stiff, self-conscious quality, as if the band had not yet relaxed into empathy, while the versions here of Denny’s “John the Gun” and “Late November” (both of which she soon rerecorded on her own) have the intuitive rapture of inspired rehearsal. Denny might have improved on her vocals in later takes, but it’s hard to hear how. She sings the traditional “Wild Mountain Thyme” like a queen in need, at once regal and yearning, and does it again, against the restrained grit of the band’s guitars and harmonies, in the closing cover, “Two Weeks Last Summer.” Written by Dave Cousins, Denny’s one-time bandmate in the Strawbs, it is a song about looking back in fond wonder at something special and fleeting — something a lot like the band that never finished this record.