PulsarGenerator Synthesis Software for Macintosh OS (review)

PulsarGenerator is a Macintosh program written in SuperCollider, a sound synthesis software system developed by James McCartney (recently made available for free at www.audiosynth.com). [Editor's Note: Installing SuperCollider is not necessary in order to run Pulsar Generator.] Available for free in a demonstration version (from www.create.ucsb.edu/Pulsar-Generator/), the full version can be purchased for US$ 49.00. The program is not officially supported, and there is no indication of any forthcoming updates. After 1 January 2003, however, the program will be distributed for free.

Figure 1.

PulsarGenerator user interface.

Written by Alberto de Campo and Curtis Roads, the program utilizes a series of pulse trains. Pulsar Synthesis is named after "the spinning neutron stars that emit periodic signals in the range of .25 Hz to 642 Hz." The program includes a Read Me file, a manual (PDF), and Help menus. These resources are moderately helpful, but for more fundamental questions about pulse train synthesis, Mr. Roads cites a few articles he has written on the topic, including "Sound Composition with Pulsars" in the March 2001 issue of the Journal of the Audio Engineering Society (Vol. 49, no. 3).

The interface for the program (see Figure 1) largely consists of 13 windows that correspond to functions controlling the various aspects of the pulse train (frequency, panning, amplitude, etc.). A 14th window allows one to add ring modulation using another PulsarGenerator file. Ultimately, I found this to be a rewarding function, resulting in some relatively complex patterns. The main window of the program allows the user to turn the sound on and off, to record the sound to disc, to control the burst ratio, as well as other functions. This window also allows the user to spawn a Table window (which permits the organization and access of different patches) and a Scope window (which is particularly helpful when dealing with sub-audio waveforms).

Besides being able to save and load wavetables, you can also draw a wavetable by Command-clicking to draw straight line segments, Option-clicking to add exponential segments, and Control-clicking to add cosine segments. Thus, any drawn wavetable can be a mixture of these three types of segments. Windows can be resized so as to draw wavetables more accurately. By clicking the "E" key, one can spawn an Edit window which indicates the various key commands available, and allows for further editing possibilities. Due to the unique approach of the program, the editing system is not the most intuitive. Once one is comfortable with it, though, wavetable editing is relatively simple, and very rewarding. One aspect of the program that is particularly useful is that most changes can be done while the sound is being played in loop mode, allowing for instant feedback.

Most of the functions of the program are accessed through two menus: Fill and Alter. The Fill menu offers "Fourier & Chebyshev" synthesis, "Phase Modulation," "Buzz" waveforms, "Grain Envelopes," and "Noise." The "Fourier & Chebyshev" synthesis function is particularly fun. One can draw amplitudes and phases for each of 40 harmonics in order to generate a complex additive waveform. One can also randomize the amplitudes of the harmonics or the phases of the harmonics. In addition, by using the "Fourier & Chebyshev" synthesis function, one can make minor changes to the harmonics of wavetables that have been drawn or have been generated by other means.

The "Phase Modulation" function allows the user to specify the Carrier Frequency, the Modulator Frequency, and the Modulation Index. The "Buzz" function allows one to enter the number of harmonics, the frequency of the lowest harmonic, and the amplitude series coefficient. The "Grain Envelope" permits Hanning, Parzen, or Welch envelope shapes.

The Alter menu offers many functions for changing wavetables, including: Normalization, Reversing, Inverting, Absolute Value, Squaring, Cubing, Distorting, Negative Clipping, Smoothing, Scaling, and Comb Filtering. Some...