OK, so we’ve all heard that the Beatles are the greatest band of all time, and I’m not saying it isn’t true, but can someone explain to me in specific terms what their musical impact was? I’m not talking about cultural impact. Nor am I seeking a list of musicians who cite the Beatles as an influence. What I want to know is: what did the Beatles do in their music that had never been done before, or at least never done nearly as effectively? What musical styles or techniques did they originate? etc.
Read Allmusic’s brief biography for an overview.
The Beatles were the first to include feedback as a specific element of a song (rather than as a recording error), in 1965’s “I Feel Fine”.
The Beatles’ album “Sgt. Pepper’s Lonely Hearts Club Band” was one of the first concept albums, and while not particularly conceptual by today’s standards- the title, the artwork, the opening song, crowd noise stuck at the beginning of the second side, and the next-to-last song; compared to such albums as The Wall and Thick As A Brick, it’s not particularly much - it’s still the most that had been done by that point.
While the Beatles did not personally invent psychidelic music, they were at the forefront of it, and many of the other bands at the forefront (The Byrds, The Beach Boys, etc.) pointed to the Beatles as groups they attempted to both imitate and out-innovate.
Some firsts that come to mind:
The Beatles used more that the standard 3 chord format. They used 6 and 7 chords in songs that were richly melodic in comparison to their peers.
The Beatles started writing songs about things other than “boy meets girl” love songs. Think about Eleanor Rigby, Taxman, Dr. Robert, etc. when other groups were still asking “Do you love me surfer-girl.”
The Beatles, well probably George Martin actually, started experimenting with different instruments, backwards tracks, alarm clocks, voices, and generally anything to add layers to the song. Studio work took over live gigs and
The Beatles pioneered the 4-man pop rock format, drums, bass, rhythm, lead which is still the most popular format today (OK maybe a lead singer who doesn’t play an instrument too, but the instruments remain the same.)
They treated the studio and the process of recording as another instrument in the band, rather than a place to capture a live recording. The established the concept of a band that exists to make studio recordings vs. recording and touring.
There are countless studio and sound-processing techniques they either did first, popularized or took in new directions.
They entrenched the guitar-driven rock band who writes their own songs as the form that mattered in popular music.
They forced the public to consider commercial pop rock music to be an art form worth the time to probe from a critical review standpoint.
They established the album as the unit of music to consider - not the single.
They set the path that defines how a pop musician is expected to progress - easily accessible pop to more sophisticated, challenging pop, to more mature explorations that retain pop sensibilities. Every modern artist’s development arc is measured against how the Beatles evolved in their short lifespan as a group.
They invented power pop as a sub-genre of rock/pop music - edgier and more sophisticatedly structured than pop, but no out-there psychedelic. See Rubber Soul.
The list goes on - they are pretty much the Alpha and the Omega and deserve all the respect they get.
I can hardly wait until some real Beatles diehards get wind of this thread. fishbicycle, why do I think you might have a POV on this? 
Before they morphed into cheeky-chappy moptops - and then into bizarrely-dressed, drugged-up, long-haired loonies - The Beatles were straight up & down rock ‘n’ rollers.
I wasn’t part of the Merseybeat scene in the early 60’s myself (I lived 250 miles away and only 3 years old) but wasn’t every band in those days a four-piece? All wearing identical suits? And playing pretty similar music?
Granted, The Beatles seemed to be the one Liverpool band that made it big but it must be remembered that Gerry & The Pacemakers had the distinction of being the first band to have UK No. 1s with their first 3 singles (“How Do You Do It?”, “I Like It” and “You’ll Never Walk Alone”) and a No. 2 with their 4th (“I’m The One”). And they were exact contemporaries with The Beatles: in fact, they were also managed by Brian Epstein.
My impression is that the Beatles were largely responsible for taking the techniques electronic music from the avant-garde scene and popularizing them. If that’s true, it counts for a lot of influence.
As with the GQ thread on why rock musicians have long hair, I don’t know whether to cry, mourn my age, or rejoice that once contentious issues are now so settled that they’re unknown matters of history.
What made the Beatles interesting and important were that they were eclectic musical sponges. Unlike many of their compatriots in England - who, from the Rolling Stones to Fleetwood Mac were blues purists - and the singers in the U.S. - who were becoming singers of standards and professional songwriter-written music - they absorbed every type and style of popular music in existence. Blues, R&B, country & western, English music hall, doo-wop, girl group, rockabilly, Tin Pan Alley, Broadway, pop, rock ‘n’ roll. Both black influences and white influences, to put it simplistically. However simplistic, too many rock critics concentrate on “black” influences and ignore the “white” ones, which is the fundamental mistake with the Beatles.
In addition, the Beatles honed their chops in Hamburg, adding more influences through the Bohemian community there and more importantly simplifying and tightening their music. Again unlike many of their contemporaries, they ditched the horn sections that drove much R&B and standards for a guitar-laden sound. The famous dismissal by Decca Records because guitar bands were on their way out is an indication of how out of step the Beatles were with contemporary hit record making. They also moved away from the lead singer with backups style to put more emphasis on harmonies and multiple leads.
The Beach Boys also did these things and were rewarded with near-instant success even before the Beatles. Their only handicap was that as much of a genius as Brian Wilson was, he didn’t have another equal mind to bounce ideas off of for a wider range. As Joe Adamson wrote of Irving Brecher’s failure to write successful Marx Brothers scripts, “His other drawback was that he was, perhaps incurably, one person.” Wilson’s songs sounded great but far more of a piece than the Beatles, who changed personalities with each new record. And they put out 16 albums in 6 years in the U.S. Forty of their songs made the top 100 in 1964. Forty. That’s as unimaginable today as it was then.
When the Beatles finally gained success, therefore, they were part of a musical movement but also a step in front of it. Especially in America their songs sounded fresh and new because they blended so many influences that none of them stood out. The uncanny catchiness of their tunes certainly helped, as did their astounding sophistication for unlearned musical oafs.
When an unnamed music critic (probably William Mann) wrote the following, almost everybody mocked him, including the Beatles:
But it’s all true. They did use pan-diatonic clusters and Aeolian cadences, even if they had no idea what they were or meant.
Just as importantly, they kept that step ahead at least through 1967. 1965 saw the progression from Help to Rubber Soul, effortlessly incorporating Dylan’s electric folk into an already softer sound. Revolver’s eclecticism defined music in 1966. “Penny Lane”/“Strawberry Fields Forever”, the greatest double A-side of all time, was recording studio wizardry that lead into Sgt. Pepper’s. When Johnny Rivers sings in “Summer Rain” that “everybody was playing Sgt. Pepper’s Lonely Hearts Club Band,” he wasn’t kidding. It wasn’t so much the individual songs as the complex layering of sound and imagery in them as a grouping that made the album the standard base of music over the single. Don’t forget that the number one songs in America prior to the release of Sgt. Pepper’s were the Supremes’ “The Happening,” “Something Stupid,” by Frank and Nancy Sinatra, and “Happy Together” by the Turtles.
By the time of the white album, the Beatles were mostly writing and sometimes recording individually and the difference can be heard. Their best and most innovative work came as a group, helped certainly by George Martin’s superb ear and producing ability, each contributing a diverse piece of musical heritage into the stew. That’s what makes the Beatles so important musically. They embodied popular music as it was known at the time and melded it into a larger and stronger body of art.
Groundbreaking studio techniques
Automatic Double Tracking (ADT)
Reverse guitar
Looped tape effects
Processed vocals
Flanging
Varispeeding
Direct Injection
They pioneered the practice of running voices and instruments through a Leslie Speaker
and many more
They were the first popular music act to use non-standard instruments: Sitar, Clarinet, etc.
I could go on, but I have to run…
I disagree with this point. The Stones may have been blues/soul/50’s rock purists at the start, but by 65-66, in a large part because of the influence of the Beatles, they had expanded their palette significantly.
How many of those were actually invented by the Beatles, and how many were already in use in electronic music? Tape looping was definitely already out there, but I don’t know about any of the others.
Bringing avante garde techniques into the mainstream (such as tape loops and sound collage) was another of the Beatles’ significant achievements. Who actually “invented” them is of secondary importance at best.
Most were brand new studio techniques never used before.
George Martin and Ken Townshend (senior recording engineer at Abbey Roads studio) were the primary inventors, but many of the techniques were instigated by suggestions from John and Paul. For example, John hated double-tracking sessions and actively sought out for a better solution, which led to ADT. Some were the result of direct experimentation by The Beatles themselves; Tape loops on “Tommorrow Never Knows”, for example.
Plus, George Martin was a Beatle. 
Oh, and the backwards guitar on I’m Only Sleeping, that was Harrison. He played the notes for the lead guitar in reverse order, then reversed the tape and mixed it in. That type of stuff had never been done before.
And Fleetwood Mac didn’t? The point is that the groups started as blues purists but then “expanded their palettes” because of influences like the Beatles. But the Beatles were never purists at any time; they started wide and went wider.
There wasn’t even a Top 40 hit off Sgt Pepper’s. Looking at the discography here: http://www.beatles-discography.com/ I see *Strawberry Fields/Penny Lane * in late Winter '67 followed by *All You Need is Love * in Summer '67 while *Sgt Pepper’s * was released in June. Back then a hit rock album without any singles was a new experience.
The Beatles didn’t originate many of the things they are credited for, but they did popularize or make such things mainstream. If they heard an interest riff played on a record or by another group, they would use it.
In the Anthology DVD set, there’s a segment where Paul, George, Ringo, and George Martin talk about this. They had people all over the studio using every machine with each playing a tape loop that John or Paul had created at home running through it. All the machines were tied into the main board and the take was made. Paul noted that it would be virually impossible to replicate the take since the loops would have to be started and played at exactly the time every time.
They were able to play parts of the track and indentify where they came from.
In the U.S., yes, but not in England. It was the custom there not to put singles onto the album so that buyers wouldn’t be purchasing the same songs twice. That’s why so many of the Beatles singles wound up outside their Capitol albums that a separate album called Hey Jude was compiled to make them all available on a 33 1/3.
*Strawberry Fields/Penny Lane * were recorded for the Sgt. Pepper sessions but they took so long that it was decided to spin those songs off as a separate single to have product during what was then an unprecedent gap.