"Fool Me Once" is just the second song powered by a vocal to reign in the chart's decade-long history, echoing a feat first earned by Sade in 2010.

In a format known primarily for its lush arrangements and sexy sax sounds, Lindsey Webster has notched a rare No. 1.

Webster's soulful "Fool Me Once" is the first fully vocals-driven No. 1 on Billboard's Smooth Jazz Songs chart (where it leads for a second week, dated March 5) since Sade's "Soldier of Love," which reigned for three weeks in February and March 2010. In the history of the radio airplay chart, which began Oct. 22, 2005, the two songs are the only all-out vocals-fueled entries to hit the top (of 132 total No. 1s).

(George Benson and Al Jarreau's "Mornin'" led for five weeks in 2006-07, but it sports scat-singing from Jarreau, as opposed to a fully defined vocal. The song is a mostly-instrumental update of Jarreau's 1983 track "Mornin'," which does boast vocals.)

Webster has more words, about her coronation.

"The fact that I'm on a Billboard chart, let alone at No. 1 ... let alone in a mostly instrumental format, has been a huge turning point for me," the Woodstock, N.Y., native says about her first entry on any Billboard ranking, from her 2015 sophomore album You Change. "Having the only other vocal No. 1 since queen Sade is an amazing thing, almost incomprehensible. I am so grateful to my partner [husband, producer, keyboardist and co-songwriter], Keith Slattery, for writing the music that inspired 'Fool Me Once.' Without him and our band turning what was just an idea into a beautiful song, we would not have what is now a No. 1 hit on Billboard!"

Webster's manager Bud Harner took on his role after becoming a fan. "When I first heard ["Once"], I was thinking, 'Is this as good as I think it is?' I literally tracked down Lindsey and Keith and said, 'You don't know me but …,'" the veteran A&R exec says. "They told me a friend had tried to get the song played on SiriusXM's Watercolors channel, but nothing had happened. I sent the song to [program director] Trinity, who added it. I then sent it to other programmers in the genre and they confirmed my initial reaction.

"Smooth jazz is primarily an instrumental-based format with some vocals thrown in here and there. Somehow I had the feeling that this song would go beyond those limitations. To see it at No. 1 is very satisfying and exciting."

Sums up Webster, "'Fool Me Once' has always been one of those songs that 'felt good,' from the writing to recording. It's great to know that other people seem to feel the same way about it."