The Delay effect that is currently shipped with Audacity has multiple problems (bug 533)

The excessive wording in the interface is inconsistent with built in effects
(this is not the only bundled plug-in with this issue, but best to clear them
one at a time)

The level of each echo is much lower than the level set by the user (the manual
has been temporarily adjusted so as to be vague rather than wrong about this).

The pitch change not only changes the pitch but also the speed of the echoes,
causing the echoes to drift out of synch with the original audio.

Missing license information in the comments (though brief license declaration
is present in the GUI).

Audio becomes stretched if the sample rate is less than 44.1 kHz

Nyquist has a pitch shift function (pitshift) that changes pitch without changing tempo, but unfortunately the sound quality of this effect is quite poor and when applied to short percussive sounds (such as a click track) it introduces a a short echo of its own
(independent of the delay effect). This is a limitation of the pitch shift function in Nyquist and is not fixable within the Nyquist plug-in code.

Until such time as there is a better quality pitch shift primitive available in Nyquist (not likely in the foreseeable future) there is really no good solution for providing a pitch-shifted echo effect in a Nyquist plug-in.

So as not to lose a current Audacity feature, I think that probably the best option is to offer a choice of either achieving the pitch change by stretching (resampling) as in the current effect, or using the Nyquist (pitshift) function. Each method has pros and cons as described.
delay2.ny (3.65 KB)

Another observable problem with Nyquist pitch shift is that it seems to cause the resultant delay time to be longer than that entered in the effect.


Yes, the Nyquist pitch shift effect applied on its own produces a delay in the output.
For example this is the code to cause a small raising of the pitch. When applied to a click the delay/echo problem with the pitch shift effect is obvious.

(pitshift s 1.1 1)

On less percussive sounds the limitation is less noticeable, especially if the echoes are substantially quieter than the “dry” sound.

Topic moved to archive as the latest version is now shipped with Audacity