TAP-plugins
Tom's Audio Processing plugins
for audio engineering on the Linux platform
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TAP Pitch Shifter

[TAP Pitch Shifter GUI as shown in Ardour]

This plugin gives you the opportunity to change the pitch of individual tracks or full mixes, in the range of plus/minus one octave. Audio length (tempo) is not affected by this plugin, since audio is completely resampled. Besides being a special effect for creating foxy guitar tracks, it may come handy if your (otherwise very attractive) singer or chorus-girl was a bit indisposed at the time of recording: with the power of Ardour automation, you are given a chance to correct smaller pitch errors.

General information

Unique ID2150
I/O ports1 input / 1 output
CPU usage (44.1 kHz)7.4%
CPU usage (96 kHz)16.3%
Hard RT CapableYes
In-place operationSupported
run_adding() functionProvided

Usage tips

There are two controls to set the same thing: you can set the amount of pitch shift by either setting the "Semitone Shift" or the "Rate Shift" control. The former is scaled in semitones, allowing you to set musically sensible pitch shift rates. The latter is scaled in percentage of the original pitch, so that is closer to a "physical", non-musical approach.

The available pitch shift range is one octave up or down. One octave downwards (-12 semitones) corresponds to a setting of -50% of the "Rate Shift" control, one octave upwards (+12 semitones) corresponds to a "Rate Shift" setting of +100%. The "Semitone Shift" control has priority over the "Rate Shift" control in a way that if "Semitone Shift" is nonzero, it determines the amount of pitch shift in itself. If "Semitone Shift" is zero, then the "Rate Shift" setting comes into play. (Note that in Ardour, setting a control back to zero is as easy as shift-clicking on it.)

You can achieve attractive effects by mixing the pitch-shifted signal together with the original: that's why the "Dry Level" and "Wet Level" controls are provided. By default, the dry signal is muted, and the wet signal is output with 0 dB, so you won't need to touch these contols if you don't want to create such a mix.

To thicken the sound of your heavy-metal guitars even further, shift them down with 12 semitones and mix that with the original sound, with a level of 2-6 decibels lower than the original. To create harmonies of a vocal track (simulating another vocalist singing the same thing a bit lower/higher), apply a pitch shift of 3 or 5 semitones to the track, and mix it to the original with a slightly lower volume.

Summary of user controls

namemin. valuedefault valuemax. value
Semitone Shift -12 0 12
Rate Shift [%] -50% 0 100%
Dry Level [dB] -90 -90 20
Wet Level [dB] -90 0 20
latency varies with sample rate
and pitch shift settings

Notes

Unfortunately, this plugin is far from being perfect. (Anyone heard of a perfect pitch shifter?) Varying amounts of phasing effects are introduced at varying pitch shift rates. The good news is, if you settle on a particular setting, the side effects of the plugin are static: no parasite tremolo, vibrato, etc. effects built in, only static attenuation of certain frequencies due to phase cancellation. That's not very lovely, but still not as confusing as some other pitch shifters with strong, time-varying side effects.



$Id: pitch.html,v 1.3 2004/08/17 13:05:16 tszilagyi Exp $