Auto-Tune, Acid Loops, Varispeed, and The Beatles

What is Auto-tune?

You may have heard of the term “Auto-Tune” before.  It was originally a piece of hardware (now it is often a piece of software run on a computer) that was invented in the late 1990s to help correct a singer’s pitch in the recording studio so that they were in tune and on key. In 1998, the singer Cher, recorded a song named Believe which used an exaggerated Auto-Tune effect that causes the vocals to sound electronic or computerized.  Basically, the effect is created by having the Auto-Tune snap the vocals sharply into perfect pitch. 

What is the Cher Effect?

A singing voice and most instruments actually go in and out of pitch naturally.  If you think of the string of a guitar vibrating, when a string is plucked it is vibrating its fastest and it eventually slows down until it stops or is muted by the player.  So when a string is plucked it is slightly sharp, and then it comes into tune and then it goes slightly flat over time. When Auto-Tune is normally used, it is adjusted to change pitch more gradually like the notes would be sung by a singer.  The Auto-Tune distortion effect (sometimes called the “Cher effect”) is created by removing the gradual attack and decay of the pitch of a note and forcing it to jump to the exact pitch unnaturally.

The “Cher effect” is often used in modern Pop and Hip Hop recordings to this day.  In fact, you may have heard to it referred to as Auto-Tune, but Auto-Tune is also used on a lot of recordings in a more natural way that you would never even notice or be able to tell it was applied if it is done correctly.

So, what’s an Acid Loop?

Also, in the year 1998 a computer program called Acid Pro was developed which allowed a music producer to take clips or loops of music and splice them together to create a song.  Music producers still use this technique today to remix old songs or create new songs.  Acid Pro used a specific format for its loops called Acidized loops, which was an audio format that included key and tempo information about the loop which made it easier for Acid Pro to take loops that were in different keys and in different tempos and change them all to the same key and tempo for a particular song. Changing the tempo of a song with a computer is called “time stretching,” because when you change the tempo it stretches the amount of time the audio clip takes to play.

Where did it come from?

Pitch correction in recording is much older than Auto-Tune, however. Recording engineers started tweaking pitch on recordings as far back as the 1940s, using a control called varispeed on reel to reel recorders. Varispeed allowed engineers to slow down and speed up a recording slightly to correct pitch. Slowing down and speeding up a tape recording will change both pitch and tempo.  Slow it down and the pitch is lower and the tempo slower.  Speed it up and the pitch is higher and the tempo faster. Naturally, you have to be careful how much you tweak parts of a recording with varispeed or the change will be two noticeable and the tempo and timing may be thrown off.  So only subtle changes can be made using varispeed.  With Auto-Tune it is much easier to correct pitch and you can do it without throwing off the tempo because a computer can change pitch and tempo independently.

What other uses does this technology have?

In 1966, George Martin, the producer of the Beatles had a problem. John Lennon wanted him to combine two different takes of the song, Strawberry Fields Forever into one final song.  The problem was that the two takes were in different tempos and in different keys.  George Martin had changed keys and tempos before on purpose before in Beatle’s songs, but this time the two takes were not purposely recorded in a particular key or tempo to make using varispeed work.  By an odd coincidence; however, it happened that the tempo and key of the slower first clip was exactly the correct so that if the tempo were speeded up to match the second clip that the key would also match.

The problem became a bit more tricky, because Martin liked the quality of Lennon’s voice in the first clip and raising the tempo and pitch would alter that, so with the help of the recording engineer Geoff Emerick the two decided to leave both clips in the different keys and tempos they were in, but just splicing the two clips together would be a noticeable and jolting cut, because such a sudden change in tempo and key would be noticeable.  So Emerick was able to transition the two clips by speeding up the last clip gradually at the end of the clip until it matched the tempo and key of the second clip. This little trick would be easy for a modern computer to do with a piece of software, but Emerick had to manually and gradually change the speed with the varispeed slider knob.  It took him a few tries to get it right, but such engineering tricks using reel to reel tape recorders are the things that software developers have used as a basis and inspiration for designing audio editing and recording software on.

Well did it work?

In 1966, when Lennon said he wanted the two different takes of Strawberry Fields Forever spliced together, he did not realize what went into it and what it would take two experienced recording professionals to do to figure out how to do it. Today, the average DAW, Digital Audio Workstation, software that can be downloaded for free from the Internet makes it possible for someone to change tempo and key with a few clicks of the mouse and a little bit of knowledge of the software.

Cher – Believe
Strawberry Fields Forever – The Beatles

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