Brainwave synchronization is a practice that aims to cause brainwave frequency to synchronize with a frequency corresponding to the intended brain state. The technique has been used to induce sleep or to treat numerous psychological and physiological conditions.

It is usually performed with the use of specialized medical software. It depends upon a “frequency following” response, a naturally occurring phenomenon where the human brain has a tendency to change its dominant EEG frequency to the frequency of a dominant external stimulus. Such a stimulus may be aural, as in the case of binaural or monaural beats and isochronic tones, or visual, as with a dreamachine, a combination of the two with a mind machine, or even electromagnetic radiation.

Brainwave synchronization has been used in one form or another for centuries, from shamanistic societies’ use of drum beats to Ptolemy noting in 200 A.D. the effects of flickering sunlight generated by a spinning wheel. In the 1930s and ’40s, with then-new EEG equipment and strobe lights, W. Gray Walter performed some of the first scientific research on the subject. Later, in the 1960s and ’70s, interest in altered states led many artists to become interested in the subject, most notably Brion Gysin who, along with a Cambridge math student, invented the Dreammachine.

From the 1970s to date there have been numerous studies and various machines built that combine light and sound. These efforts were aided by continued development of micro circuitry and other electronic breakthroughs allowing for ever more sophisticated equipment for measuring and inducing brainwave synchronization. One of the most important breakthroughs was the discovery of binaural beats, first published in Scientific American in 1973 by Gerald Oster. With the development of isochronic tones by Arturo Manns, combined with more sophisticated equipment, these discoveries led to many attempts to use brainwave synchronization in the treatment of numerous diseases and disorders.

Booker T. Jones is an instrumentalist, songwriter and arranger, best known for fronting the band Booker T. and the MGs. He has also worked in the studios with some of the most highly regarded artists of our time, earning him a Grammy Award for lifetime achievement.

Jones was a child prodigy, playing the oboe, saxophone, trombone, and piano at school and serving as organist at his church. He attended Booker T. Washington High School with future stars like Isaac Hayes’s writing partner David Porter, and Earth, Wind, and Fire’s Maurice White.

Booker T. & the MGs are an instrumental R&B band that was influential in shaping the sound of Southern Soul and Memphis Soul. For many years, the official story was that the bandname The MGs was meant to stand for Memphis Group, not the sports car of the same name. However, this proved not to be the case, as musician and record producer Chips Moman, active in Stax Records when the band was formed, claims they were named after his car.

In June of 1967, they appeared at the Monterey Pop Festival, alongside performers like Jimi Hendrix, Janis Joplin, The Who, and Jefferson Airplane. They were also later invited to play Woodstock, but drummer Al Jackson, Jr. was worried about the helicopter needed to deliver them to the site, and so they decided not to play.

The Mexicali Brass were apparently created by Crown Records, a subsidiary of the Bihari Brothers’ Modern Records, in order to cash in on the popularity of Herb Alpert & The Tijuana Brass and The Baja Marimba Band during the 1960s.

Teddy Phillips, the band’s leader, graduated from Oak Park River High School, where he had learned to play the sax in school band. After graduation, he toured with many bands and also worked in radio studio bands for both NBC and CBS

He formed his own band in 1944, the Teddy Phillips Orchestra, which played at local Chicago clubs until 1947, when he played the Aragon Ballroom. The band was a fixture there and at the Trianon and Willowbrook Ballrooms became the best known band in town. Curiously, his popularity came just as the Big Bands era was closing.

By the 1960s, he had transformed the band into the Mexicali Brass, a Las Vegas style Mariachi Band. During the 1970s, he contined performing with the band, and toured the USA briefly.

Bert Kaempfert was a German orchestra leader and songwriter. He made easy listening and jazz oriented records and wrote the music for a number of well-known songs, such as Strangers in the Night and Spanish Eyes.

He was born in Hamburg, Germany, where he received his lifelong nickname, “Fips”. He studied at the School of Music and was hired by Hans Busch to play with his orchestra before serving as a bandsman in the German Navy during World War II. He later formed his own big band, toured with them, then worked as an arranger and producer.

One contributor to Kaempfert’s music was guitarist-bassist Ladislav “Ladi” Geisler, who popularized the famous “knackbass” (crackling bass) sound, which became the most distinctive feature of many Kaempfert recordings. It is a treble staccato bass guitar sound in which the bass string is plucked with a pick and immediately suppressed to cancel out any sustain.

Tahitian Sunset was sampled extensively by the lo-fi dance artists Lemon Jelly as their track In the Bath.

Cymatic therapy is a scientifically unsupported alternative medicine technique using acoustic waves which was developed in the 1960s by Sir Peter Guy Manners. It is based on the assumption that human cells, organs, and tissues have each a natural resonant frequency which changes when perturbed by illness.

Starting in the sixth century BC, Greek philosopher Pythagoras was the first to use music to heal a person’s body and emotions. During the eighth century, German scientist Ernst Chladni proved that sound does affect matter. Chlandi, the father of acoustics showed that as he drew a bow across the edge of a metal plate covered with sand, the sand moved and formed geometric patterns.

Cymatic therapists apply different audible frequencies and combinations of sound waves which they claim entrain malfunctioning components back to their healthy vibratory state and promote natural healing. The operational principle of cymatic therapy is out of step with mainstream scientific thought, and it is viewed with skepticism by most medical doctors. Relying on this type of treatment alone, and avoiding or delaying conventional medical care, may have serious health consequences.

Cymatic therapy is operationally, historically, and philosophically distinct from the many medical uses of ultrasound and from the more mainstream practice of music therapy.

Comfort noise is artificial background noise used in radio and wireless communications to fill the silence in a transmission resulting from voice activity detection or from the audio clarity of modern digital lines.

Some modern telephone systems such as wireless and VoIP use voice activity detection, a form of squelching where low volume levels are ignored by the transmitting device. In digital audio transmissions, this saves bandwidth of the communications channel by transmitting nothing when the source volume is under a certain threshold, leaving only louder sounds such as a speaker’s voice to be sent. However, improvements in background noise reduction technologies can occasionally result in the complete removal of all noise.

The result of receiving total silence, especially for a prolonged period, has a number of unwanted effects on the listener, including the following:

• The listener may believe that the transmission has been lost, and therefore hang up prematurely.
• The speech may sound choppy and difficult to understand.
• The sudden change in sound level can be jarring to the listener.

To counteract these effects, comfort noise is added, usually on the receiving end in wireless or VoIP systems, to fill in the silent portions of transmissions with artificial noise. The noise generated is at a low but audible volume level, and can vary based on the average volume level of received signals to minimize jarring transitions.

In modern VoIP products, users may control whether they want comfort noise enabled or disabled. During the siege of Leningrad in 1942, the beat of a metronome was used as comfort noise on the Leningrad radio network, indicating that the network was still functioning.

Earworm is a term for a portion of a song or other musical material that repeats compulsively within one’s mind, known colloquially as “music being stuck in one’s head”. The Germans use the word Ohrwurm (rhymes with “door worm,” where the “w” is pronounced like a “v”) to denote these cognitively infectious musical agents. Use of the English translation was popularized by James Kellaris and Daniel Levitin.

Kellaris’ studies demonstrated that different people have varying susceptibilities to earworms, but that almost everybody has been afflicted with one at some time or another. The psychoanalyst Theodor Reik used the term “haunting melody” to describe the psychodynamic features of the phenomenon. Another scientific term for the phenomenon, involuntary musical imagery, was suggested by the neurologist Oliver Sacks in 2007.

People with obsessive-compulsive disorder are more likely to report being troubled by ear worms. In some cases medications can minimize the effects. Earworms should not be confused with endomusia, which is a serious affliction in which someone actually hears music that is not playing externally.

Binaural beats or binaural tones are auditory processing artifacts, or apparent sounds, the perception of which arises in the brain independent of physical stimuli. This effect was discovered in 1839 by Heinrich Wilhelm Dove.

The brain produces a phenomenon resulting in low-frequency pulsations in the loudness of a perceived sound when two tones at slightly different frequencies are presented separately, one to each of a subject’s ears, using stereo headphones. A beating tone will be perceived, as if the two tones mixed naturally, out of the brain. The frequency of the tones must be below about 1,000 to 1,500 hertz for the beating to be heard. The difference between the two frequencies must be small, below about 30 Hz, for the effect to occur; otherwise, the two tones will be heard separately and no beat will be perceived.

Binaural beats are of interest to neurophysiologists investigating the sense of hearing. Second, binaural beats reportedly influence the brain in more subtle ways through the entrainment of brainwaves and can be used to produce relaxation and other health benefits such as pain relief.

The effects of binaural beats on consciousness were first examined by physicist Thomas Campbell and electrical engineer Dennis Mennerich, who under the direction of Robert Monroe sought to reproduce a subjective impression of 4Hz oscillation that they associated with out-of-body experience. On the strength of their findings, Monroe spawned the binaural self-development industry by forming The Monroe Institute, now a charitable binaural research and education organization.

In addition to lowering the brain frequency to relax the listener, there are other controversial, alleged uses for binaural beats. For example, that by using specific frequencies an individual can stimulate certain glands to produce desired hormones. Beta-endorphin has been modulated in studies using alpha-theta brain wave training, and dopamine with binaural beats. Among other alleged uses, there are reducing learning time and sleeping needs. Some use them for lucid dreaming and even for attempting out-of-body experiences, astral projection, telepathy and psychokinesis. Alpha-theta brainwave training has also been used successfully for the treatment of addictions and for the recovery of repressed memories.

An uncontrolled pilot study of Delta binaural beat technology over 60 days has shown positive effect on self-reported psychologic measures, especially anxiety. Another claimed effect for sound induced brain synchronization is enhanced learning ability. It was proposed in the 1970s that induced alpha brain waves enabled students to assimilate more information with greater long term retention. In more recent times has come more understanding of the role of theta brain waves in behavioural learning.