Collin Morikawa followed his 61 with a clean carded 6-under 64 to earn the lowest 36-hole score at East Lake and a share of the lead with Viktor Hovland heading into the weekend of the FedEx Cup finale.
Morikawa's round gave him the course record that had belonged to Tiger Woods.
"Sometimes just being out there when you don't realise that you're out there for that long of a period, but you find one thing that you hope works," said Morikawa, winless since the DP World Tour Championship in Dubai at the end of 2021.
"I've done that for the past few years, hoping that we're going to find that one thing that clicks and right now, I'm going to stick with it."
Scores can look inflated at the Tour Championship because players start at various points under par depending on the FedEx Cup position. Looks were not the least bit deceiving with Morikawa, who shot 125 without a bogey over two days of extreme heat.
He was No.24 in the FedEx Cup and started at 1-under par. Hovland, who has been hotter than Atlanta dating to the final round in the BMW Championship last week, was the No.2 seed and began the tournament at 8 under.
They now are 16-under par, two shots clear of top seed Scottie Scheffler. The world No.1 was running hot under the collar after opening with a 71 that included the worst kind of triple bogey - a tee shot in the water and a three-putt from 15 feet.
But Friday was another ball-striking clinic - he missed only two greens - and Scheffler made enough birdie chances for a 65.
"I was six shots better," Scheffler said. "I didn't hit it in the water on 15, and I had three less three-putts, so there you go."
That's about the only simple math in the FedEx Cup, that and the $18 million to the winner.
Woods shot 127 for the opening 36 holes in the 2007 Tour Championship, back when everyone started at even. That was the year grass was hard to find on the putting surfaces and the pins were in the middle of most greens.
This year it's all about the wind, or lack of it. The heat has been stifling, but only an occasional breeze has allowed for extreme scoring. Five players shot 65 or lower.
"There's going to be a lot more low scores, a lot more birdies made. I'm going to have to continue that heading into the next two days," Morikawa said.
Keegan Bradley, doing what he can to make those six wild-card picks even tougher for Ryder Cup captain Zach Johnson, birdied three of his last five holes for a 67 and was at 13-under.
Masters champion Jon Rahm (65) and Xander Schauffele (64) were four shots behind.
Former world No.1Jason Day had an even-par 71 to remain at four under.
The Queenslander is the lone Australian at East Lake and is tied 19th, 12 behind the leaders.