It's not a colorful plastic egg filled with candy hidden in the grass on Easter morning. Some may not even be child-friendly.

It's not as easy as rubbing a genie in a bottle, but with a little searching, you can find secret messages hidden in the music you love to listen to. Whether just for fun or to make a statement, artists have been known to embed secret codes or “Easter eggs” in their albums.

Really, it is not a modern phenomenon at all. Composers of classical music like Mozart and Bach were known to slip subliminal messages called cryptograms into their scores. Mozart had a secret code of numbers that he used in letters to his family and in his music in order to prevent censorship. Bach often inserted a signature (using the notes B-A-C-H) into his pieces.

The first Easter eggs in the modern era were literally plastic eggs. The term Easter egg is believed to have originated with the movie, “The Rocky Horror Picture Show.” The cast and crew had an Easter egg hunt on the set, and, needless to say, a few Easter eggs were missed and appear throughout the film.

Nowadays, the term can refer to any hidden reference in a work of art, piece of music, movie or elsewhere. Though we may be most familiar with Easter eggs in films, such as the hanging in the background of the Wizard of Oz or secret nudity in The Little Mermaid, music tracks are full of hidden treasures.

In the days of vinyl, artists like The Beatles would lock grooves on their records so that the turntable would begin to turn in a continuous loop. Others used inverse grooves that caused the needle to fly off the record. Only by placing the needle at what appears to be the end of the track will the Easter egg be played.

In modern music, the most common technique is backmasking or hiding a message that can only be heard when played in reverse. At one point, this was quite controversial, as it was associated with the occult. This method is also used to edit profanity out of songs played on the radio.

Just like no one may know what Mona Lisa’s smile means, so we may never know what these artists were trying to say. But you can have fun hunting down these Easter eggs with an old record player, CD player or even a spectrograph.

 10. Sgt. Pepper’s Lonely Hearts Club Band– The Beatles

The Beatles taught us that all you need is love, but that love may not extend to our furry friends. If you wondered why your dog howled every time you played the band's album, "Sgt. Pepper's Lonely Hearts Club Band," the answer lies in a high-frequency sound inserted at the end of the record that is only audible to your canine companion.

Nobody knows exactly why the Beatles chose to insert this extra sound. It certainly wasn't to please PETA. A dog may be man’s best friend, but apparently it isn’t a two-way street.

9. The Wall – Pink Floyd

They say that what comes around goes around. This is the case on Pink Floyd’s album “The Wall.” The opening track contains a voice saying, “We came in.” The end of the last track has the same voice saying, “Isn’t this where?” When the album is played on a continuous loop, the voice says, “Isn’t this where we came in?”

We're not sure if the band was struggling with their entrances or if they became fascinated by boomerangs on their Australian tour. Either way, they definitely came full circle.

8. Sterálfur – Sigur Rós

Pop bands from Iceland aren't exactly a dime a dozen, and neither are songs from Icelandic band Sigur Rós. High school literature teachers all over the world should be thankful by showing that what you learn in class can actually have practical applications.

The band’s track “Starálfur” is written palindromically. Whether it is played backward or forwards, it still sounds the same.

Are you at the end or just beginning? You may never know. Now that’s a bit more impressive than “a man, a plan, a canal, Panama.”

7. YYZ – Rush

Unlike The Police, Rush was not trying to send an S.O.S. to the world, but the band was well-versed in Morse code. In the intro to their song, “YYZ,” the song’s title is played by Morse code.

In case you haven’t memorized your Morse code or airport codes, YYZ also happens to be the code for Toronto’s Pearson International Airport. It was a jet plane he was leaving on, bound for the capital of the province of Ontario, which, not so ironically, is also the city where the Canadian band was formed.

6. Daddy – Korn

If you listen past the silence on Korn’s track “Daddy,” you will hear a tape recording of a domestic dispute. While not exactly a surprising find, given that the lyrics of the song talk about abuse in the home, what may be shocking is that the recording is not contrived.

The producer Ross Robinson claims to have found the tape in an abandoned apartment. If he was trying to make a statement about domestic abuse, he definitely hit home.

5. The Great Gig in the Sky – Pink Floyd

Sometimes selective listening is a good thing. If you are having an existential breakdown, you may want to avoid Pink Floyd’s “The Great Gig in the Sky.” If you listen closely at 3:35, you can hear the words, “If you hear whispering, you’re dying.”

Talk about casting a spell on someone. After hearing that message, you might want to pinch yourself to make sure you are still alive and avoid walking under any ladders.

4. I Remember Larry – Weird Al

It should come as no surprise that Weird Al can be a little on the strange side. What you probably didn’t know is that his song “I Remember Larry” contains the backward phrase, “Wow, you must have an awful lot of free time on your hands.”

Weird Al probably had a bit too much time on his hands to mix that in.

3. Erased, Over, Out – Nine Inch Nails

They say that artists are often their own worst critics. This may be the case with Nine Inch Nails’ “Erased, Over, Out.”

When you press the fast-forward button on your CD player while playing the track, you will hear the command, “Erase me,” being repeated over and over again. How the song ever made it onto the album, we may never know.

2. Empty Spaces – Pink Floyd

In an era when artists were being accused of satanic conspiracies, Pink Floyd apparently wanted revenge. In their track "Empty Spaces," the group backmasked the message, “Hello, hunters. Congratulations. You have just discovered the secret message. Please send your answer to Old Pink, care of the Funny Farm, Chalfont.”

It's not clear what kind of fan mail they received in response. Nevertheless, they filled in the empty spaces and got their message across – loud and clear.

1. [Equation] – Aphex Twin

Perhaps the most disturbing and hardest-to-find Easter eggs are created through a technique called spectral imaging. By using a spectrograph, images can be converted into audio files. An artist wanting this image to appear during the music just has to mix the resulting “musical image” into the track.

If you happen to have a spectrograph on your hands (or a computer program capable of deciphering spectrograms), you can project the hidden images.

Aphex Twin’s “[Equation]” was the cause of much controversy when a spectrograph revealed what very much resembled a demon.

It wasn’t until later that Jarmo Niinisalo discovered that the face was not a disturbing demon but Richard D. James – the Aphex Twin himself. That is one way of paying homage to yourself.

Sources:huffingtonpost.com, academia.edu, cracked.com, twistedsifter.com