With multiple Grammy wins and the nickname of the “nicest guy in Nashville,” it’s no wonder Vince Gill is the guy most people call when they’re looking for a pitch-perfect country collab. Gill has collaborated with countless artists over his decades-long career. He estimated this number to be upwards of “seven, eight, nine hundred” musicians during a Q&A session at his Guitar Center RockWalk induction ceremony in 2016.

While speaking of his extensive collaborative career, Gill also mentioned a couple of country icons who fulfilled his childhood dreams and challenged him in new ways. Unsurprisingly, the artist whom he had always dreamt of working with as a child was Merle Haggard. Gill was a child of the 1960s and 70s, which was the peak of Haggard’s popularity. And although Haggard never lived in Oklahoma, his family’s roots were there. And that further connected him to Gill, an Oklahoma native.

Gill sang four songs with Haggard on a new album that the latter country icon was producing just before his death in April 2016. His passing was still two months away when Gill talked about the country collab at the Guitar Center event, describing Haggard as his “all-time hero.”

Previously, Gill cited Haggard as the greatest country music artist of all time during an interview with Dan Rather. “He epitomized everything I wanted to try to be,” Gill said. “He’s a great singer, an amazing guitar player. A lot of people don’t understand how good a musician Merle is.”

Vince Gill Said This Particular Country Collab Was the Most Challenging

As an elite, top-of-the-call-list kind of player, Vince Gill has had no small shortage of musical opportunities to explore during his prolific career. A talented vocalist and an even more impressive guitarist, Gill has offered his musical skills in various capacities over the years. Each one has provided Gill a chance to learn and grow as a musician. During his 2016 Q&A session, Gill said one of the hardest country collaborations he ever did was with the pot-smoking, Trigger-playing, Redheaded Stranger, Willie Nelson.

“The hardest job I’ve ever had in my whole life was to sing harmony with Willie Nelson,” Gill said at his RockWalk induction ceremony. “I don’t know if you’ve ever tried it, but it’s not easy.”

Whether because of Nelson’s particular phrasing or the fact that it was difficult for Vince Gill to get over his starstruck attitude toward Willie Nelson, the “When I Call Your Name” cited this country collab as his most difficult. But in that same breath, it was also incredibly inspiring.

Speaking to The Lakeland Ledger in 2013, Gill said he found Nelson to be incredibly inspiring, especially in his older age. “I’ve watched him at the age where you think you would probably start slowing down. He’s done the exact opposite,” Gill said. “I’m starting to get the feeling like I’ve only got so many good years left. I really want to make as much of a statement as I can.”

Of course, if Nelson is any indication, Gill has plenty more notes to play.