Objective

FM synthesis creates rich spectra from only two sinusoidal oscillators, and is able to emulate the sound of many physical musical instruments. John Chowning's seminal publication on audio-range frequency modulation (FM) in 1973 describes a number of different orchestral instruments such as woodwinds, brass, and percussion that can be created merely by adjusting a few basic parameters of the basic FM equation.

In this mini-project, implement several different Chowning FM instruments and compare them to the sounds of physical instruments. Also develop code to model the Chowning algorithms as LabVIEW virtual musical instruments (VMIs) to be "played" by a MIDI file within MIDI JamSession.

Prerequisite Modules

If you have not done so already, please study the prerequisite modules FM Mathematics and Chowning FM Synthesis Instruments in LabVIEW. If you are relatively new to LabVIEW, consider taking the course LabVIEW Techniques for Audio Signal Processing which provides the foundation you need to complete this mini-project activity, including working with arrays, creating subVIs, playing an array to the soundcard, and saving an array as a .wav sound file.

Deliverables

Part 1: Chowning FM Instruments

Chowning FM Synthesis Instruments in LabVIEW provides the specifications for a generic FM synthesis instrument, parameters for a number of different instruments, and a screencast video that walks through the complete process to implement the Chowning clarinet in LabVIEW. Refer to the PDF document in that module that contains the parameters for the remaining instruments: bell, wood-drum, brass, and bassoon. Create your own LabVIEW implementation of each of these four instruments (the clarinet VI is available in that module, as well).

Save a representative sound from each of the five Chowning instruments to a .wav file.

Part 2: Comparison with Physical Instruments

Visit the Musical Instrument Samples database created by the Electronic Music Studios of the University of Iowa at http://theremin.music.uiowa.edu/MIS.html. These recordings of actual instruments were made inside an anechoic chamber to eliminate reflections and other artifacts, so the spectra of the instruments are as accurate as possible. The files are stored in AIFF format; use an audio editor such as Audacity to import the AIFF format. Audacity also includes a tool to view the spectra of the soundfile.

Compare and contrast the FM sounds you created for brass, clarinet, and bassoon to those of the real instruments. Consider time-domain envelope shape and spectrogram patterns.

Part 3: Chowning VMIs for MIDI JamSession

In this part, convert each of the five Chowning instruments you implemented in Part 1 into its own virtual musical instrument (VMI for short) that can be played by "MIDI JamSession." If necessary, visit MIDI JamSession, download the application VI .zip file, and view the screencast video in that module to learn more about the application and how to create your own VMI. Your VMI will accept parameters that specify frequency, amplitude, and duration of a single note, and will produce a corresponding array of audio samples.

You may wish to keep all of your existing front-panel controls available so that you can listen to your VMI during development. Adjust the parameters to obtain pleasing and realistic settings, and convert the front-panel controls to constants and remove all indicators. Your finished VMI must not contain any front-panel controls or indicators beyond those provided in the prototype instrument.

Finally, choose a suitable MIDI file and use MIDI JamSession to play your FM VMIs. MIDI files that contain multiple channels are ideal, because you can individually assign each of your five VMIs to a different instrument.

Create a .wav file of your finished work.