featuring True Voice | for iOS devices

designed to help reduce stuttering

how it works

MasterPitch modifies the natural mouth-to-ear acoustic feedback such as to replicate the “chorus effect”. This effect is observed when a stutterer sings in a chorus or speaks in unison with a second speaker, under which circumstances stuttering is virtually eliminated or strongly reduced.

unique features of MasterPitch

MasterPitch has a unique feature allowing FAF to be chosen from two alternatives:
Basic and TrueVoice.

TrueVoice consists of a patent-pending algorithm allowing to preserve the idiosyncrasies of the voice when the pitch is altered. The resulting voice quality gives the comfortable sensation that the speaker is either younger or older.

For comfortable listening in noisy environments, MasterPitch provides a Noise Gate functionality which, if selected, virtually eliminates the disturbance caused by the noise when there is no voice activity.

Due to microphone and hearphones characteristics, volume should be adjusted such that sound level is comfortable and the Altered FeedBack is more audible than the natural acoustic feedback

In order to provide effective Altered Feedback, MasterPitch requires the use of hearphones inside-the-ear, or covering the ears, such as to make the Altered FeedBack more audible than the natural acoustic feedback.

MasterPitch is an application for the iPad and iPhone platforms


MasterPitch is a product developed by:

SEEGNAL Research

Estrada Circunvalação, 10078, 2DTO
4465-084 S. Mamede Infesta

and distributed by:


Rua Pêro de Alenquer, 230

4150-615 Porto


masterpitch alters

the acoustic feedback

in two ways:

Frequency Altered Feedback (FAF)

The voice sound is modified in pitch before reaching the ears, as if a different person was speaking, or the same person but younger or older.

Delayed Altered Feedback (DAF)

The voice sound reaches the ears later than the natural acoustic feedback; the delay can be adjusted between 40 milliseconds and 500 milliseconds.

MasterPitch comes

with three presets

with options for

lower/higher pitch
and volume adjustment:


fluency-enhancer app