It's easy for older Willie Nelson fans to overlook his modern works, where he saw his influence dig out tributaries away from the safer riverbeds. In the past two decades, he has ventured out from his hearty country roots into reggae, spooky Daniel Lanois-produced noir, pop standards, Spanish-tinted passages and flirted heavily with new-school Americana with Ryan Adams.

Rocks Off is continuously fascinated with the man, even more so in the past few years. At one point he was merely a nostalgia act for some. This past creative period has seen the artist become an all-encompassing musical animal able to grab onto to any genre and make it his own, or at least paint pictures with it using his own unique brush.

"Highwayman" and "Always On My Mind" are as standard now as "I Want To Hold Your Hand" and "Blitzkrieg Bop" around these parts, so it's refreshing to see an artist still undergoing his own metamorphosis as he nears octogenarian territory. That's why we wish Johnny Cash had started working with Rick Rubin way earlier instead of towards the end of his days as a mortal.

Teatro

1998 saw Nelson working with Daniel Lanois at the producer's converted theater in Oxnard, Calif. Lanois converted an old movie theater into a recording studio to help create the mournful and echoey sound that he has cultivated since his days collaborating with Brian Eno on various U2 albums and in his own solo work. Teatro came on the heels of Bob Dylan's Time Out Of Mind, and both saw each artist reaching late age and looking back on life. Backing vocals from Emmylou Harris seal the deal on this stellar outing.

Spirit

Nelson self-produced this utterly funereal 1996 release with a distinct Spanish guitar lilt. At times it's heart wrenching, with most songs sounding ready-made for a wake or the final goodbye from a widower sitting graveside.

American Classic

Rockers like Rod Stewart veered off for albums of pop standards by the early '00s. Last year, Nelson did the same in his own set of versions of expertly crafted pop from the days when songs were built to last. His take on cuts by Johnny Mercer and Lerner & Loew are fun stuff, and a nice change from the Vegas-style razzmatazz that Rod the Bod poured all over them.

Songbird

Ryan Adams & the Cardinals were always a severely Nelson-influenced group of musicians, and in 2006 both teams joined forces for a project of mammoth proportions. Adams assumed production duties, and the Cardinals backed Nelson over seven covers and four originals by the two principals. A special standout is the crack group's take on Leonard Cohen's "Hallelujah."

Countryman

It took decades for Willie to fully embrace the air of pot smoke around him in song, and in 2005 he finally did with this set of island-ready tracks. A Jimmy Cliff tune and reggae-fied Cash track set the tone. A version of "I've Just Destroyed the World," a song that Nelson and Ray Price wrote, seems to float above the Kingston clouds like delicious smog. Going back and listening to the original, it already has a rock-steady vibe to it in a way.

With John Evans, 8 p.m. Saturday, January 9, at the Arena Theatre, 7326 SW Fwy., 713-772-5900 or www.arenahouston.com.