. >> woodruff: for those stations staying with us-- renowned singers robert plant and alison krauss recentlylbum, and plan to tour internationally this summer. jeffrey brown caught up with them in nashville. here is an encore of their conversation, part of our arts and culture series, "canvas." ♪ ♪ ♪ >> brown: a visit to sound emporium, one of nashville's most renowned recording studios, where alison krauss and robert plant recorded their new album, "raise the roof"-- and, on this day, got to admire the cover for the first time. ♪ trouble with my lover i'm in ♪ trouble ♪ >> brown: it's a musical marriage of two legendary voices from two very different worlds. ♪ i'm in a world of trouble ♪ >> where i come from, the blend is what you're always going for. you know, you try to match how --one voice, is the goal. and this is the complete opposite. >> from a vocalist point of view, at the sharp end of the various kinds of adventures i've had, the whole thing is about, just, "go!" and we'll worry about it later. ♪ ♪ ♪ >> brown: he, now 73, is rock 'n roll royalty. ♪ ♪ ♪ the quintessential howler an