Some of the “heroes” of Willie Nelson’s latest album, who either collaborate with the music legend or contribute songs to the project, seem sorta dubious: two of his sons, Sheryl Crow, Coldplay. (Though we totally get Snoop Dogg, who joins Nelson, Kris Kristofferson, and Jamey Johnson on “Roll Me Up and Smoke Me When I Die.”) But Nelson has been bending the rules of popular music for half a century now, so the LP’s concept is just mere dressing. After all, this is a guy who once threw together an album to pay off his IRS debt. Heroes gathers 14 songs — some date back to the ’30s, some are brand-new originals — pairing Nelson with artists of various wattage. Best are two contemporary covers, Pearl Jam’s “Just Breathe” and Coldplay’s “The Scientist,” which rank among Nelson’s finest in recent years.