Sound, Consonance, and Dissonance Lecture

Introduction to Sound

Definition of Sound
- Sound is a variation of air pressure (vibration of air).
- Particles in the air alternate between compression and rarefaction, propagating waves similar to water ripples.
- No sound propagation in space due to the absence of air particles.
Human Perception of Sound
- Vibrations affect the eardrum, and the brain interprets these as sound.

Frequency of Oscillation
- Sounds are compared based on their frequency ratios.
- Simpler frequency ratios result in more consonant (pleasing) sounds.
Examples of Consonance
- 220 Hz and 440 Hz (ratio 2:1) are very consonant.
- 220 Hz and 660 Hz (ratio 3:1) and 220 Hz and 880 Hz (ratio 4:1) are also consonant.
Harmonic Series
- The sequence of frequencies where each subsequent frequency is a whole multiple of the fundamental frequency.
- Simpler ratios ensure more frequent wave synchronization, leading to consonance.
Beating in Dissonance
- Dissonant sounds create a beating effect due to waves slowly syncing and then desyncing.

Creation of Scales
- Most consonant intervals (ratios like 3:1 and 2:1) are used to create scales.
- Example: Constructing a pentatonic scale (5 notes per octave).
- The pentatonic scale is widely used in various musical genres globally.
- A scale's first note is termed the tonic.
Major and Minor Scales
- Relative minor scale uses the same notes as the major scale but starts from a different tonic.
- Example: C Major and A Minor scales share the same notes.

Detailed Look at Harmonics
- Harmonics 2, 4, and 8 are octaves; harmonics 3 and 6 are the fifths and thirds.
- The purity of consonance is indicated by the absence of beating.

Fundamental Frequencies and Overtones
- A sound comprises a fundamental frequency and its overtones.
- Harmonic overtones align with the harmonic series, while inharmonic overtones do not.
- Inharmonic sounds lack clear pitches (e.g., snare drum, cymbal).
Waveforms and Overtones
- Sine Wave: No overtones.
- Square Wave: Contains odd harmonics.
- Sawtooth Wave: Contains all harmonics.
- White Noise: Equal levels of all frequencies, 20 Hz to 20 kHz.

Overtones and Instrument Tone
- Overtones affect the timbre of an instrument.
- Different instruments sound distinct due to varying overtone compositions.
Practical Examples
- Visual representation of harmonic and inharmonic tones in instruments.

Consonance in Major and Minor Scales
- Consonance hierarchy: fifths, fourths, thirds, and sixths.
- Harmonic series alignment with scale notes.
Instrument Tuning Using Harmonics
- Historical context: Pythagorean temperament and its imperfections.
- Development of various temperaments, leading to the equal temperament system used today.

Triads and Extended Chords
- Basic triads: Root, third, fifth.
- Extended chords: Adding sevenths, ninths, elevenths, etc.
- Examples of major, minor, augmented, diminished, and power chords.

Common Cadences
- Authentic Cadence: 5 - 1.
- Plagal Cadence: 4 - 1.
- Half Cadence: Ends on 5.
- Deceptive Cadence: 5 - 6.
Chord Progressions in Popular Music
- Construction of chord progressions using cadences.
- Example progression creation, using random chords and cadences.

Scales and Modes Comparison
- Modes derived from scales, creating unique interval structures.
- Examples of constructing scales like the Lydian, Dorian, and Phrygian modes.
Exotic Scales
- Examples: Byzantine, Messiaen's, and acoustic scales.

Complex Chords and Inversions
- Understanding and using chord inversions.
- Differences between inversions and root positions.
Special Chords
- Neapolitan Sixth, Picardy Third, and other special chord types.
Harmonic Sequences and Modulations
- Techniques for moving between different keys and building complex harmonic structures.

Importance of Understanding Sound and Harmony
- Comprehensive understanding improves musical composition and appreciation.
- Encourages experimentation and deeper exploration of harmonics and scales.