Accomplish the indicated achievement to get the corresponding number of Gamerscore points:

A Little Help From My Friends (10 points): Start a Story with a four player band.
All You Need Is Love (30 points): Five-star every song in The Beatles: Rock Band.
All Together Now (15 points): Get a Guitar, Bass and Drum unison bonus on the songs listed on the Achievements screen.
In Seconds Flat (15 points): Maintain Beatlemania for 60 seconds.
Shake It Up, Baby! (10 points): Use Beatlemania at least 5 times in a single song using either Bass or Guitar.
Eight Days A Week (10 points): Get an 8x Band Multiplier.
Like a Million Suns (20 points): Score 1,000,000 points in a single song.
Authenticity (10 points): Finish any song as a Bassist with Lefty Mode turned on, hitting at least 50% of the notes.
How Could I Dance with Another? (20 points): Score 100% playing I Saw Her Standing There on Expert Bass.
Day Tripper (15 points): Start a new Story save file and reach the credits within 24 hours.
I GOT BLISTERS ON MY FINGERS! (35 points): Score 100% notes hit on Helter Skelter playing Expert Drums.
Let's Get Some Levels (5 points): Calibrate your system for the optimal experience.
Better Free Your Mind Instead (35 points): Earn Expert gold stars on the 4 songs displayed on the Achievements screen.
Things That Money Just Can't Buy (35 points): Earn Expert gold stars on the 4 songs displayed on the Achievements screen.
No One's Frightened of Playing (35 points): Earn Expert gold stars on the 4 songs displayed on the Achievements screen.
And the Band Begins to Play (35 points): Earn Expert gold stars on the 4 songs displayed on the Achievements screen.
Elmore James Got Nothing on This (25 points): Get 85% or better on all solos in The Beatles: Rock Band on Expert Guitar.
Still My Guitar Gently Weeps (30 points): Hit 100% of the notes in either of the solos in While My Guitar Gently Weeps on Expert Guitar.
What I Got I'll Give to You (30 points): Hit 100% of the notes in the solo of Can't Buy Me Love on Hard or Expert Guitar.
Sun, Sun, Sun Here It Comes (25 points): Get a 350-note streak playing Here Comes The Sun on Guitar.
Goo Goo G'joob (25 points): Get a 550-note streak playing I Am The Walrus on Drums.
The Words You Long to Hear (20 points): Earn a five-star rating for the songs on the Achievements screen as a Vocalist on Hard or Expert.
She Still Sings It with the Band (25 points): Get all possible Double Fab ratings for every song with 2 vocal parts.
All the Children Sing (25 points): Get all possible Triple Fab ratings for every song with 3 vocal parts.
Won't You Come Out to Play? (25 points): Play Dear Prudence on Expert Guitar, playing all hammer-ons and pull-offs without strumming.
Liverpool Lads (10 points): Play a song in The Cavern '63 in Story.
Really Big Show (10 points): Play a song on The Ed Sullivan Show '64 in Story.
Stadium Superstars (10 points): Play a song in Shea Stadium '65 in Story.
The Final Tour (10 points): Play a song in Budokan '66 in Story.
In the Studio (10 points): Play a song in Abbey Road, Studio 2 in Story.
Passed the Audition (20 points): Play all the songs on the Apple Corps Rooftop '69 in Story.
Mr. K Will Challenge the World (10 points): Finish all 8 Chapter Challenges.
Toppermost of the Poppermost (15 points): Finish all 8 Chapter Challenges with full star ratings.
I Saw the Photograph (10 points): Get your first Beatles Photo.
Teachers Who Taught Me WERE Cool (15 points): Complete all the Beatle Beats.
That's It! You've Got It! (25 points): Get a 350-note streak playing Hey Bulldog on Bass.
Pick a Moon Dog (25 points): Play Dig A Pony on Expert Guitar, playing all hammer-ons and pull-offs without strumming.
Doing the Best That You Can! (20 points): Complete all the Drum Lessons.
Gear Guitarist (20 points): Earn a Guitar Career score of 1,000,000.
Ace Bassist (20 points): Earn a Bass Career score of 1,000,000.
Dazzling Drummer (20 points): Earn a Drum Career score of 1,000,000.
Sensational Singers (20 points): Earn a Vocal Harmonies Career score of 1,000,000.
Do Right by Me (25 points): Get a 350-note streak playing Ticket To Ride on Guitar.
We Would Be So Happy, You and Me (25 points): Play Octopus's Garden on Expert Guitar, playing all hammer-ons and pull-offs without strumming.

Additionally, there are six secret achievements:

Don't Let Me Down (10 points): You saved a bandmate from failing!
Oh Yeah, All Right! (30 points): Hit 100% of the notes in the solo of The End on Hard or Expert Guitar.
Are You Gonna Be In My Dreams? (35 points): Hit 100% of the notes in the solo of The End on Expert Drums.
In Penny Lane There Is A Barber (10 points): Get half of the Beatles Photos.
The Love You Make (10 points): Complete the Encore in Story.
Images of Broken Light (20 points): Get all the Beatles Photos.