The Beatles basically began as an air-tight autonomous unit. Besides a rare pre-fame credit for Tony Sheridan, their early records were presented as band efforts.

Toward the end of their time together, however, they began to welcome key outsiders into the sessions – and by the time the Beatles launched individual solo careers, the studio doors were flung wide open.

Some of those later projects don't make clear designations as to who – besides the Beatles themselves, of course – did what as sidemen. Still, their albums were dotted with key collaborators, some of them very famous.

Our list of the Top 10 Guest Performances on Beatles songs takes in both discographies, together and apart, while making some notable exceptions. We didn't include "Rockestra Theme" from Wings' 1979 album Back to the Egg, simply because it's overstuffed with guest stars – including everybody from David Gilmour and John Bonham to Ronnie Lane and Pete Townshend. There wouldn't be room for anybody else.

We also left out songs where producer George Martin made key contributions, including his sped-up Bach-influenced turn at the piano for 1965's "In My Life," because he really can't be counted as a guest. Our focus was on rock songs, so we likewise discounted jazz guys who contributed to so many of Paul McCartney's songs over the years.

Along the way, our look back at the Top 10 Guest Performances on Beatles songs found at least one instance where a different musical perspective improved upon the initially released version:

10. Phil Collins, "Art of Dying"
From: George Harrison's All Things Must Pass (1970)

Maybe Phil Collins was fated to appear on a Beatles record. After all, he appeared as a teen extra during the climactic concert sequence for 1964's A Hard Day's Night. Like many of the songs on George Harrison's Wall of Sound-inspired debut, "Art of Dying" takes an echo-laden rock-orchestra approach. Somewhere beneath the rumbling sounds made by most of what would become Derek and the Dominos – not to mention future "Dream Weaver" hitmaker Gary Wright - is Collins, credited with "percussion." Sessions for All Things Must Pass began in May and continued through October 1970. By then, Collins had taken over the drum chair with Genesis.

9. The Band, "Sunshine Life for Me"
From: Ringo Starr's Ringo (1973)

Ringo Starr, like his collaborators here in the Band, had a penchant for roots music – and they never got more countrified than on "Sunshine Life for Me." Former Beatles bandmate George Harrison actually wrote the song, then gave way to Rick Danko, Levon Helm, Garth Hudson and Robbie Robertson in the studio. They turn the track into a good-time hootenanny, very much in the style of the Band's "Rag Mama Rag," despite its sad undertones. "Sunshine Life for Me" is subtitled "Sail Away Raymond," in reference to one of the lawyers representing the Beatles' warring factions. Starr would later invite Danko, Helm and Hudson along for his first All-Starr Band tour.

8. Elvis Costello, "You Want Her Too"
From: Paul McCartney's Flowers in the Dirt (1989)

The meeting that would help halt McCartney's '80s-era creative slide was decidedly low key. Elvis Costello joined him in an old British corn mill that McCartney had converted into a personal studio. They sparked, as Costello reanimated something that had been largely dormant since McCartney's split with the similarly acerbic John Lennon. At least 16 songs have emerged from their brief partnership, in every form from radio singles ("My Brave Face," "Veronica") and album deep cuts to expanded-reissue extras. The Sgt. Pepper-ish "Mistress and Maid" began after McCartney brought in a postcard of a Vermeer painting and said, "Let's write this story."

7. Frank Zappa, "Jamrag"
From: John Lennon's Sometime in New York City (1972)

Taken from an encore performance with the Mothers of Invention in June 1971 at the Fillmore East, "Jamrag" later appeared as an "original" on a Lennon solo record. This came as a surprise to Frank Zappa, since they were actually playing a ragged version of "King Kong" from his 1969 album Uncle Meat. "I don't know whether it was Yoko [Ono]'s idea or John's idea," Zappa complained on an interview picture disc, "but they changed the name of the song to 'Jamrag,' gave themselves writing and publishing credit on it, stuck it on an album and never paid me." Zappa later released a portion of the "King Kong" section from the Fillmore East on 1992's Playground Psychotics.

6. Steve Winwood, "Love Comes to Everyone"
From: George Harrison (1979)

A song reflecting Harrison's life of domestic bliss at the time, "Love Comes to Everyone" opened his 1979 self-titled album and then reached the Billboard Adult Contemporary Top 40 after being released as its second single. Eric Clapton makes the next of three appearances on our list of Top 10 Guest Performances on Beatles Songs, plucking along during the intro. But Clapton's ex-Blind Faith bandmate Steve Winwood becomes a dominant voice, employing an array of new keyboard sounds that would subsequently leverage 1980's Arc of a Diver into a breakout solo hit.

5. Elton John, "Whatever Gets You Thru the Night"
From: John Lennon's Walls and Bridges (1974)

Elton John famously wagered that this song would become Lennon's belated first solo chart topper after dropping by during the sessions for Walls and Bridges. If it did, Lennon would have to join him onstage at Madison Square Garden. Then one of the hottest acts in rock, Elton John helped that process along by adding keys and a backing vocal. When "Whatever Gets You Thru the Night" knocked Bachman–Turner Overdrive's "You Ain’t Seen Nothing Yet" off the top of the Billboard Hot 100 in November 1974, John collected on the bet: A trio of duets with him later that month became Lennon's final concert appearance.

4. David Gilmour, "No More Lonely Nights"
From: Paul McCartney's Give My Regards to Broadstreet (1984)

This wasn't McCartney's first collaboration with David Gilmour (that would be 1979's "Rockestra Theme") or his last (Gilmour was also part of the sessions for 1999's Run Devil Run). It remains, however, his most commercially successful. "No More Lonely Nights" was recorded live in a single three-hour session at Elstree Film Studios, a lightning-fast process that stunned the more fastidious Gilmour. McCartney then released the single in advance of a movie that ended up a huge flop. Good thing: Momentarily free of associations with Give My Regards to Broadstreet, "No More Lonely Nights" became one of McCartney's last Billboard Top 10 singles.

3. Billy Preston, "Get Back"
From: The Beatles' Let It Be (1970)

Billy Preston stopped by Apple to see George Harrison, and was quickly recruited to join the tension-filled sessions for "Get Back." "It's interesting to see how nicely people behave when you bring a guest in, because they don't really want everybody to know that they're so bitchy," Harrison said in Anthology. "He got on the electric piano, and straight away there was 100 percent improvement in the vibe in the room." On the song, too. That earned Preston a rare Beatles guest credit, as "Get Back" went to No. 1 in the U.S. and U.K.

2. Cheap Trick, "I'm Losing You"
From: John Lennon's Anthology (1998)

Frustrated by an inability to get Yoko Ono on the phone while away in Bermuda, Lennon recalled the hurt and rage from their '70s-era "Lost Weekend" separation and channeled that into this song. Producer Jack Douglas then had an inspired notion to bring in Cheap Trick guitarist Rick Nielsen and drummer Bun E. Carlos, with whom he'd worked on At Budokan, to complete things. Only somewhere along the way, Lennon lost his nerve. Another version, this time featuring his regular working band, ended up on 1980's Double Fantasy, the last album issued in Lennon's lifetime. The far-superior Cheap Trick take went unreleased until 1998's Anthology.

1. Eric Clapton, "While My Guitar Gently Weeps"
From: The Beatles (1968)

Clapton began a lifetime of musical collaborations with Harrison by recording an uncredited, song-making solo on "While My Guitar Gently Weeps" for the Beatles' ironically titled 1968 album. They were never less of a band. Unable to get the others on board, Harrison purposely brought Clapton into the sessions in order to get the group back on track – just as he would again a few months later with Billy Preston. That must have been a relief to all involved, since Harrison had already burned through an entire eight-hour session trying to do his own solo.



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