DIY beat-frequencies

If two different sound waves approach your ears at different frequencies, the difference between the frequencies produces a ‘interference tone’ or ‘difference tone’.  Saying it another way, two tones tuned slightly away from each other result in an differential ‘multiphonic’ tone.  This tone has an audible ‘beating’ effect.  See binaural beating.  Beat frequencies are also heard if two instruments are playing in unison, yet slightly ‘out of tune’ from one another thus creating a beat-frequency of the difference between the two frequencies.  They can also be tuned to target brainwave frequencies for an experience known as brainwave entrainment.

f_beat = ( f₁ − f₂ )

This is worthy of exploration within a music composition:  Two dimensions giving birth to a third.  Mix in some form of rhythmic vibrato and you’d be adding isochronic-like beats, opening up even more possibilities.  Typically these effects are produced by some sort of computer software such as Gnaural, or this plug-in for Audacity.  Needless to say there are many ways to create these effects with electronics.  However, dedication is required to compose with this effect in mind for live, acoustic musicians who have a strong command over their instrument.  It would certainly add more sonic color using real instruments as opposed to the static nature of sine waves and the like.  This is fertile territory for introspective expression.

Brainwave frequencies:

• 40⁺Hz Gamma Waves (wakeful problem-solving)
• 20-40Hz High Beta Waves (fear, anxiety, OCD and addiction)
• 12-20Hz Beta Waves (analytic thought patterns, adult consciousness)
• 10-12Hz High Alpha Waves (meditative states, visualization, relaxed optical system)
• 8-10Hz Alpha Waves (deep meditative state, resonant frequency of the Earth)
• 4-7Hz Theta Waves (enhanced creativity and spontaneity)
• 1-4Hz Delta Waves (deep sleep, dominant brainwave activity in infants)

Online searches for these beating terms results in a lot of junk to sift through.  Mostly self-help sites trying to sell you some sort of meditation soundtrack that claim to make you “meditate like a monk”, which is clearly off topic.  Beating effects are simply a phenomena of nature that can be synthesized by electronics or manifested by instrumentalists.

Here is a short binaural beating sample I made using Gnaural so that you can get and idea what it sounds like.  Listening through headphones is recommended to experience the full effect:

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Click here to download this example in .zip file.  Included is a MP3 file of the audio and the .gnaural file.  One may modify the code within the .gnaural file, just use a text editor such as Text Wrangler.  In this example, I used whole number Lo Shu derived tones (that is, numerical values with a digit sum of either 3, 6 or 9 translated into frequencies).  For more info on Lo Shu, see these related posts.