Ringo Starr's role as a glue guy in the Beatles was confirmed once they began solo careers. Long after the group split, his individual sessions drew far-flung former members back together once more.

Along the way, the affable drummer came to dominate the list of Top 25 Partial-Beatles Reunion Songs. Seven tracks come courtesy of Starr's solo projects; he's also a regular presence on tracks with George Harrison, John Lennon and Paul McCartney.

At least half the Beatles are present for many of these tracks, and in several instances three of the four ex-bandmates appear. The most famous are the so-called "Three-tles" reunion songs in the '90s, as the others came together to complete a pair of the late Lennon's songs.

Other notable partial reunions date from just after the group's 1970 breakup through modern-era collaborations as recent as the '10s. Several even include classic-era producer George Martin.

Keep reading to find out what came out on top as we count down the Top 25 Partial-Beatles Reunion Songs.

25. "Walk With You"
From: Ringo Starr's Y Not (2010)

A rare duet with McCartney, this track finds the friendly bravado of Starr's best early records melting into an intimate melancholy — and not the put-on, aw-shucks kind so familiar from his youthful Beatles performances. Instead, "Walk With You" features perhaps the darkest, most mature chorus of any Starr solo song.

24. "Average Person"
From: Paul McCartney's Pipes of Peace (1983)

"Average Person" took a long and winding road to completion, beginning as a Wings track and initially featuring Dave Mattacks on drums. But when McCartney couldn't coax out the right balance of absurdity and fun, he and returning Beatles producer George Martin brought in a ringer. Or more, particularly, a Ringo.

23. "Early 1970"
From: Ringo Starr single (1971)

The lyrics admit that Starr can't play bass, or even the piano (unless "it's in C."), opening the door for guest turns by Harrison and longtime Beatles associate Klaus Voormann. Harrison also plays electric guitar and a mean slide on this winking honky-tonk delight.

22. "Free as a Bird"
From: The Beatles' Anthology 1 (1995)

Completing a Lennon demo wasn't as easy as adding bass, guitar and drums. Producer Jeff Lynne had to find a way to correct the pacing of the old tape, so the others could sync up. That process tends to make the results feel draggy and metronomic. Still, Harrison's solo is a wonder of bundled-up emotion.

21. "Back Off Boogaloo"
From: Ringo Starr single (1972)

Fired up after sharing the stage at the Concert for Bangladesh, Starr and Harrison raced back into the studio to record this single. Co-written and produced by Harrison, "Back Off Boogaloo" was inspired by a turn of phrase from T. Rex's Marc Bolan and works itself up into an appropriately glam-rocky lather. Then Harrison gets all Duane Allman.

20. "Not Such a Bad Boy"
From: Paul McCartney's Give My Regards to Broad Street (1984)

A surprisingly straightforward moment on a bloated and often wrongheaded project, "Not Such a Bad Boy" recalls McCartney's teddy-boy days both in the lyrics and its skiffle-type guitar figure. Who better to nail things down than his old pal Starr?

19. "So Sad"
From: George Harrison's Dark Horse (1974)

Starr took part in a 1972 session where Harrison delved into the wreckage of his complicated relationship with Pattie Boyd. Perhaps thinking better of being so nakedly honest, Harrison sat on "So Sad" for years. By the time it finally appeared on 1974's Dark Horse, Alvin Lee of Ten Years After had already released his own version.

19. "Mother"
From: John Lennon's Plastic Ono Band (1970)

Lennon switched from guitar to piano as he worked out this anguished cry for lost parents, with Starr providing a smartly economical, fill-free rhythm that only adds to the lyric's stabbing emotion. Lennon recorded the shredding finale in single-line takes to save his voice. His pain is simply excruciating.

17. "Beautiful Night"
From: Paul McCartney's Flaming Pie (1997)

As with "Average Person," it took McCartney several tries – and a late assist from Starr and George Martin – to finish "Beautiful Night." He walked to Abbey Road Studios on the day they scored Martin's surging orchestral parts, traversing the famous crosswalk completely unnoticed.

16. "King of Broken Hearts"
From: Ringo Starr's Vertical Man (1998)

Harrison contributed a crying slide performance here, while producer Mark Hudson's Beatles-inspired strings give "King of Broken Hearts" an anthemic swoon – like "Act Naturally" meets "Strawberry Fields Forever." All of that might have engulfed a lesser performance from Starr, but instead he rises to the challenge, singing with a billowing sadness. This is perhaps his finest vocal.

15. "All Those Years Ago"
From: George Harrison's Somewhere in England (1981)

The first song featuring Harrison, McCartney and Starr since 1970's "I Me Mine," and the last until "Free As a Bird," was defined by Lennon's murder. Harrison wrote an early version for Starr, who demoed it but ultimately passed. After their bandmate was killed, Harrison kept Starr's drum parts but erased his vocal, updated the lyrics and then added backing vocals when McCartney stopped by for a visit.

14. "Real Love"
From: The Beatles' Anthology 2 (1996)

The so-called "Three-tles" got back together a year after completing "Free as a Bird," this time with a finished demo by the late Lennon. The results were more successful as a record, but the others ultimately had less to do – meaning the gorgeous "Real Love" tended to come off like a well-produced Lennon solo turn. Harrison declined to participate in any further reunions.

13. "Gimme Some Truth"
From: John Lennon's Imagine (1971)

Demoed during the sessions that produced 1970's Let It Be, "Gimme Some Truth" melds Lennon's love of wordplay with his knack for an excoriating takedown. As Lennon rails against the hypocrisy and villainy of the day, Harrison can be found brutally sawing on his guitar.

12. "Wanderlust"
From: Paul McCartney's Give My Regards to Broadstreet (1984)

Taking inspiration from the name of a yacht where Wings were recording London Town, McCartney originally envisioned this standout Tug of War track as a collaboration with Harrison. (Their meeting to discuss it instead produced a vocal turn by McCartney on "All Those Years Ago.") Later, McCartney invited Starr to a leaner re-recording session with George Martin.

10. "My Sweet Lord"
From: George Harrison's All Things Must Pass (1970)

Harrison initially gave away "My Sweet Lord"; it first appeared on frequent Beatles collaborator Billy Preston's Harrison co-produced Encouraging Words. He later returned to the track, crafting the first post-Beatles No. 1 song with the help of Starr and producer Phil Spector's typical cast of thousands.

11. "How Do You Sleep?"
From: John Lennon's Imagine (1971)

Half of the Beatles took part in this savage assault on McCartney, as Lennon made biting references to "Yesterday," Sgt. Pepper's Lonely Hearts Club Band and McCartney's solo hit "Another Day." So, is "How Do You Sleep?" a low point in their very public post-split bickering? Or one of Harrison's coolest-ever turns on the slide? Answer: yes.

9. "Photograph"
From: Ringo Starr's Ringo (1973)

Starr got off to a hot solo start, stringing together eight Top 10 Billboard singles between 1971-75. None of them was played more than "Photograph," which shot to No. 1 in four countries and Top 10 in seven others with a huge assist from Harrison. Starr's producer, Richard Perry, added some thundering Spector-ish elements to complete things.

8. "Take It Away"
From: Paul McCartney's Tug of War (1982)

Starr's unmistakable "backward" fills opened this ebullient single, which became an intriguing percussion duet with do-anything sessions ace Steve Gadd. George Martin played electric piano in the studio and during the fun promotional clip, which includes a parting shot from McCartney's only live performance between 1979 and 1985.

7. "Wreck of the Hesperus"
From: George Harrison's Cloud Nine (1987)

Taking a title from a poem by Henry Wadsworth Longfellow, Harrison casts a winking glance at his newfound status as a dinosaur rocker in this galloping deep cut. Starr was, of course, the perfect choice to drum up a sense of humorous self-effacement.

6. "I'm the Greatest"
From: Ringo Starr's Ringo (1973)

This lyric would have made Lennon, its author, seem like a jerk. Hand the same lines to Starr, however, and suddenly "I'm the Greatest" doesn't feel blatantly boastful. Instead, it unfolded with a sense of sardonic wit as the drummer recalled being part of "the greatest show on Earth" – before adding wistfully, "for what it was worth." Harrison's presence made this the only time the threesome worked together after the Beatles split.

5. "I Found Out"
From: John Lennon's Plastic Ono Band (1970)

Starr's rugged cadence tends to get lost amid Lennon's torrential rebuke of false idols. But those kill shots aimed at politicians, drugs, religion ("from Jesus to Paul"), parents, society – you name it – could have missed if not for Starr's pistons-firing presence.

4. "Beware of Darkness"
From: George Harrison's All Things Must Pass (1970)

Starr may be one of the few drummers who could so successfully navigate Harrison's unusual song structure on the ethereal, darkly involving "Beware of Darkness." It's the musical opposite of "I Found Out," as Starr traded stalwart aggression for the deftest of touches during brilliantly handled overlapping album sessions with his ex-bandmates.

3. "It Don't Come Easy"
From: Ringo Starr single (1971)

Starr returned to rock just one hour after he finished mixing 1970's standards-focused Sentimental Journey album, setting up at EMI with Harrison and producer George Martin. "It Don't Come Easy" lived up to its title, however, as it initially took the Harrison-directed backing group approximately 20 takes to nail the basic track. Work continued from February through October; the single didn't finally appear until April of the next year.

2. "When We Was Fab"
From: George Harrison's Cloud Nine (1987)

Harrison and Starr poke some good-natured fun at the Beatles' Summer of Love-era excesses, allowing co-producer Jeff Lynne to play every psychedelic card in the deck – adding strings, backward tapes and, of course, a sitar. The delightful video included an actor miming McCartney's left-handed bass while wearing a walrus costume; Beatles road manager Neil Aspinall also passes by at one point with a copy of Lennon's 1971 album Imagine.

1. "Instant Karma"
From: John Lennon's single (1970)

Harrison's guitar is somewhere deep in the mix of the first Beatles solo song to sell a million copies; he doubles Lennon's piano too. But his most notable contribution arrives as the Spector-produced "Instant Karma" builds to its soaring conclusion: Harrison directed the group vocals. Lennon was so thrilled with the results that he gave Spector the long-shelved Beatles tapes that became Let It Be.

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