---

Overview

“Simple” effect units operate on individual audio samples without considering one audio sample’s relationship to another, and without using a processing buffer. You build such an effect unit in this chapter, further simplified by leaving out some advanced audio unit features: a custom view and custom properties.

Simple effect units can do very basic DSP, such as:

• Change level

• Add tremolo

Monaural tremolo is a continuous wavering produced by varying an audio channel’s gain at low frequency, on the order of a few Hertz. This figure illustrates monaural tremolo that varies from full gain to silence:

Stereo tremolo is similar but involves continuous left/right panning at a low frequency.

In this chapter you design and build a monaural tremolo effect that uses the generic view. The steps, described in detail in the following sections, are:

1. Install the Core Audio development kit if you haven't already done so.

2. Perform some design work, including:

   • Specify the sort of DSP your audio unit will perform

   • Design the parameter interface

   • Design the factory preset interface

   • Determine the configuration information for your audio unit bundle, such as the subtype and manufacturer codes, and the version number

3. Create and configure the Xcode project.

4. Implement your audio unit:

   • Implement the parameter and preset interfaces.

   • Implement signal processing—the heart of your audio unit.

5. Finally, validate and test your audio unit.

Your development environment for building any audio unit—simple or otherwise—should include the pieces described under “Required Tools for Audio Unit Development” in the “Introduction.” You do not need to refer to the Xcode documentation or the Core Audio SDK documentation to complete the tasks in this chapter.

---