In this lab, you will answer some questions about modulation synthesis (part 1), as well as write a function to play FM sounds (part 2). Your deliverables will be a .txt file with your answers to the lab questions, as well as a .wav file of your FM function's output and the code that created the .wav file. Place these files in your /Library/220a/hw3/ directory.

For the composition, you will use the FM function from the lab to demonstrate the perceptual phenomena of "auditory streaming". "Submission" entails placing an HTML file hw3.html that links to your code and .wav file in your /Library/Web/220a/ subdirectory. As usual, make sure that your submission is timestamped on the Homework Factory.

Assume that the frequency of a carrier signal is 1200 Hz and the frequency of a modulation signal is 700 Hz. What are the frequencies of two sidebands in Amplitude Modulation? What is the upper limiting factor on their gain?

1. When will FM synthesis generate inharmonic spectra?
2. As a rule of thumb, what is the number of significant sideband pairs in FM?

The block diagram to the right (Figure 6.14 in the Computer Music Tutorial) shows a more elaborate FM instrument than the one seen in classes.

Follow along with the lab code to learn to implement this instrument in ChucK: hw3-playFM.pdf. Note that this time, the walk-through is not quite as step-by-step as the previous labs. At this point, you should be feeling more comfortable with ChucK to fill in the gaps. Refer to previous labs, the ChucK book, or to online documentation for help.

Your deliverable is a single .wav file, following the specifications of the FM parameters at the top of the PDF file, titled LASTNAME_playFM.wav.

The phenomenon of auditory streaming is a fascinating one. It is the process by which your mind groups information into independent objects. In music, often your mind groups objects for you over time - hence you being able to listen to a band and follow the lines of the different instrumentalists somewhat independently! Here's a visual analogy - the mind groups together the objects for you:

In this assignment, you'll be using the FM instrument that you already wrote in the lab (encapsulated in a class), to create multiple different sound sources, that then help to perceptually segregate different sound sources to the ear.

Download the starter code, and create an auditory illusion that you like - perhaps one that maximally segregates the voices: hw3-starter.ck.

We'll be listening to hear the effect of the slower tones blossoming into illusory polyphonic lines with increase speed and differentiation through other sonic parameters. Choose your own dimension(s) for the effect e.g., timbral, spatial and/or envelope qualities. In addition, make it a musical study in which the illusion is present but it's not the only interest. Concoct at least one big musical change (your choice of what that is, but it should be obvious to the listener) and shoot for a total duration of under 1 minute.

Submit to the Homework Factory an HTML file titled hw3.html that includes the following:

• Links to all ChucK files you used and wrote in your composition.
• A link to your .wav file.
• A short description of how your piece and your thoughts behind your composition.

• Rewrite the function and/or your composition using the Web Audio API.
• Write a patch that demonstrates bell, percussion, or brass sounds using FM synthesis. You can refer to Chowning's original FM paper for hints as to how to construct this.