Described Auditory Content

Described Auditory Content
An Introduction with Examples in Java

Computer Science Department

bernstdh@jmu.edu

Introduction

Describe Frequencies:
- "A" is the name commonly given to the frequencies 55Hz, 110Hz, 220Hz, 440Hz, 880Hz, 1760Hz, etc...
- The complete set of frequencies in a single octave is usually denoted by the letters A-G followed by either a sharp (half-step up) or flat indicator (half-step down)
Describe Durations:
- Commonly given as multiples/fractions of a base duration (called a whole note)
- Common durations are half notes, quarter notes, eighth notes and sixteenth notes.
- A standard duration can be "dotted" to indicate that it should be increased by 50%.
Describe the Voice/Instrument:
- Usually a name

Introduction (cont.)

A "Quick Start"

Presenting Described Auditory Content:
- The Musical Instrument Digital Interface (MIDI)
Original Purpose:
- A protocol for passing musical events between electronic instruments and sequencers (devices that stored these events)
Our Interest:
- The software portion of the protocol designed to work with files

A "Quick Start" (cont.)

Package:
- midi
Device Classes:
- Synthesizer (a device for generating sound waves)
- Sequencer (a device for reading/writing MIDI events)

A "Quick Start" (cont.)

A "Quick Start" (cont.)

Playing MIDI Files javaexamples/auditory/described/MidiPlayer.java

Presenting Described Audio

Presenting Described Audio (cont.)

Obtain a Synthesizer object by calling the MidiSystem.getSynthesizer() method
Get a Soundbank object (e.g., by calling the Synthesizer object's getDefaultSoundBank() method)
Call the Synthesizer object's loadAllInstruments() method (passing it the Soundbank object
Get the MidiChannel objects by calling the Synthesizer object's getChannels() method

Presenting Described Audio (cont.)

One Way:
1. Obtain a Receiver object by calling the Synthesizerobject's getReceiver() method
2. Construct a ShortMessage object that turns the note on
3. Call the Receiver object's send() method (passing it the ShortMessage object)
4. Wait the appropriate amount of time
5. Construct a ShortMessage object that turns the note off
6. Call the Receiver object's send() method (passing it the ShortMessage object)
Another Way:
1. Call the MidiChannel object's noteOn method
2. Wait the appropriate amount of time
3. Call the MidiChannel object's noteOff method