Nyquist Basics: Adding a Delay Effect
| This page explains how to use Nyquist to add a feedback delay effect in Audacity.
Adding a Feedback Delay Effect to an Audacity Track
To add a feedback delay effect to an Audacity track with Nyquist, the easiest way is to use the Nyquist "feedback-delay" function:
(feedback-delay sound delay feedback)
The "feedback-delay" function applies feedback delay to sound. The delay must be a number (in seconds). The sample rate is the maximum from sound and feedback (if feedback is also a sound). The amount of feedback should be less than 1 to avoid an exponential increase in amplitude. Also since output is truncated at the stop time of sound, you may want to append some silence to sound to give the filter time to decay.
1. First either load a sound file into Audacity or create an audio track within the menu.
2. Now click. A window with a text field will appear where you can type in:
;;"(sine 440)" generates a sinusoidal sound wave at 440Hz to be used as the feedback (feedback-delay *track* 0.7 (sine 440))
After clicking "OK" in the "Nyquist Prompt" window the "feedback-delay" function will take the Audacity sound and return a output sound with a feedback delay of 0.7s throughout the sound. The result of the last computation of the Nyquist code always gets automatically returned to Audacity.
Try "feedback-delay" with longer or shorter delay times as well as different sounds for feedback. Nyquist provides many more functions to generate sounds besides the simple "sine" function. Look at Functions: Sound Synthesis for the complete list of these functions.