qdts
qdts is a package for Max that, through mathematical methods and neural networks, generates Quadratic Difference Tone Spectra with controllable timbral characteristics. In doing so, it enables the creation of rich “absent” sounds—perceptual phenomena that are heard despite not being physically present in the acoustic signal—emerging from a complex of pure tones.
qdts has been featured in several artistic and academic contexts, including album releases, installations, conferences and journals. See some higlighted examples below.
Under certain circumstances, when two pure notes are played, a third one can be heard eventhough it doesn't exist. This "ghost note" is a psychoacoustic trick called an Auditory Distortion Product (ADP). Depending on how these frequencies interact, they are classified as Quadratic or Cubic Difference Tones (QDT and CDT), and over the past decades, scientists have studied them in detail.
While a single difference tone is a curiosity, a Quadratic Difference Tone Spectrum (QDTS) is a completely synthetic anomaly. Instead of synthesising one ghost tone out of a pair of other pure tones, a complex of pure tones is used to generate an entire series of illusory tones. This creates a rich and perceivable complex harmonic spectrum, even though it exists entirely inside your head.
The main caveat of QDTS is that the acoustic tones needed to generate a full spectrum of absent tones are not ordered in a harmonically logical way, which makes them challenging to use in musical practice.
To install qdts simply download the latest release from the link below, unzip the file, and move the resulting folder to your Max packages directory (typically /Documents/Max 8/Packages on macOS or \Documents\Max 8\Packages on Windows).
qdts is available for free on GitHub. You can download the latest release from the link below.
If you use qdts, please cite it as (click to copy to clipboard):