Keeping track of the line-up of Yes is almost a full-time job.

The British supergroup has had many different configurations over the years, as members come in and out, working on side and solo projects, almost on a revolving door basis.

The latest edition of Yes will be on display at Penn's Peak Friday night. The performance is sold out, according to The Peak's website.

A check of the old Classic Rock scorecard is necessary to see who is currently in the band, and it reveals the line-up is the same one that toured in 2009, including a show at Musikfest in Bethlehem last August.

Original founding bassist Chris Squire has been the one constant in the many different versions of Yes over the years, and he remains with the current edition, which also includes long-time members Steve Howe on guitar and Alan White on drums.

Keyboardist Oliver Wakeman is actually a Yes legacy, as his father, Rick, has been in Yes on and off over the years.

On vocals, Yes is now featuring Canadian singer Benoit David, who had performed in a band called Mystery as well as a Yes tribute band called Close to the Edge.

Benoit David and Oliver Wakeman joined the group in November, 2008 as fill-ins for Rick Wakeman and long-time singer Jon Anderson, whose soaring vocals have long been a part of the signature sound of many of Yes' best known songs. Reportedly, the band had planned a 40th anniversary tour that year but both Anderson and Rick Wakeman had some health problems that prevented them from going on the road.

The current quintet was part of the In The Present Tour in 2008-09, and last October, Squire reportedly announced in a radio interview that Benoit and Oliver are now full-fledged members.

No matter who has been in the line-up, Yes has enjoyed worldwide success since its inception in London in 1969 with a variety of styles, ranging from progressive rock, symphonic stylings, classical dabblings and even shorter, more pop-oriented songs during the 1980's.

The original group evolved from a British band called Mabel Greer's Toyshop and included Squire and Anderson, along with guitarist Peter Banks, drummer Bill Bruford and organist Tony Kaye. This version released two albums (Yes and Time and a Word) before Steve Howe replaced Banks for The Yes Album, which features classic material such as "Yours is No Disgrace" "Starship Trooper" and "I've Seen All Good People".

In 1971, Kaye was out, although he has returned over the years, with Rick Wakeman, formerly of the band Strawbs, taking over on keyboards as Yes released the Fragile album, featuring the hit "Roundabout". That album was the first to feature the distrinctive artwork of Roger Dean, who designed the band's logo.

For most of the 1970's, Yes was considered the poster child for progressive rock, with some of its albums (Close to the Edge, Relayer) featuring just three lengthy, multi-part songs. Line-up-wise, Rick Wakeman left, was replaced by Patrick Moraz and came back, while Bruford, who went on to King Crimson, was replaced by Alan White, who had been in John Lennon's Plastic Ono Band.

A big change for Yes came in 1980 when the British duo The Buggles, Trevor Horn and Geoff Downes, replaced Anderson and Wakeman for the Drama album. Horn would eventually become a producer, including for Yes, but Downes and Howe went on to form another supergroup, Asia, with ex-King Crimson singer John Wetton and Emerson, Lake and Palmer drummer Carl Palmer a year later.

In 1982, Yes morphed once again, adding Trevor Rabin on guitar and joining up with Kaye once more for the 90125 era. This line-up, which included Anderson, Squire and White, went on to much commercial success during the vanguard of the MTV generation, producing hits such as "Owner of a Lonely Heart", "Love Will Find a Way", "Leave It", and "Rhythm of Love", with more of a rock edge.

There have been more versions and spin offs since then, including Anderson, Bruford, Wakeman and Howe, as well as the "Mega-Yes" Union tour and album which featured eight alumni.

Asia has even celebrated a 25th anniversary and has toured, including a pair of shows at The Peak. Asia even opened for Yes last year.

The Yes Story is one that still has chapters being written.