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Principles of Sound and Music Theory

Jul 23, 2024

Concepts in Sound and Music Theory

What is Sound?

  • Sound is a variation of pressure that moves through the air; a vibration of air.
  • Particles in the air get compressed and stretched, propagating sound waves.
  • No sound in space: no particles to be compressed/stretched, hence no sound.
  • Vibrations make the eardrum vibrate, engaging the brain to perceive sound.

Consonance and Dissonance

  • Frequency of oscillation: Determines if two sounds are consonant or dissonant.
  • Simple Ratios: More consonant. Example: 220 Hz (simpler ratio 2:1 is 440 Hz).
  • Harmonic Series: Sequence created by simple frequency ratios.
  • More consonant sounds sync more often; dissonant sounds create beating (waves in/out of sync).
  • Purity of consonants: Absence of beating when two sounds play together.

Musical Scales and Music Creation

  • Octaves: Multiplying/dividing a frequency by two yields the same note, different pitch.
  • Pentatonic Scale: Five notes per octave, used globally (Chinese, blues, country, folk music).
    • Example: D major pentatonic scale: D, E, F#, A, B.
  • Major Scale: Built on systematic intervals (whole/half steps).
  • Relative Minor Scale: Shares same notes as major scale, but starts on a different note.
  • Modes: Various scales derived from a starting note, giving each unique sound.

Harmonics and Overtones

  • Harmonics: Whole-number multiples of the fundamental frequency.
    • Guitar strings: Vibrate to produce fundamentals and harmonics.
    • Natural Harmonics: Isolate specific harmonics by touching string at precise points.
  • Inharmonic Overtones: Not part of harmonic series, affect tone, common in percussive sounds (snare, cymbal).

Sine, Square, and Sawtooth Waves

  • Sine Wave: Only fundamental frequency.
  • Square Wave: Fundamental + odd harmonics.
  • Sawtooth Wave: Fundamental + all harmonics.

Temperament and Tuning Systems

  • Pythagorean Temperament: Based on pure fifths, favored perfect fourths/fifths in Occidental music.
  • Minton Temperament: Pure thirds, adjusting fifths slightly.
  • Equal Temperament: Modern system; divides octave into 12 equal parts, enables modulation to any key.

Chords and Harmonization

  • Triads: Basic chords with root, third, and fifth.
    • Variants: Major, minor, augmented, diminished.
  • Seventh Chords: Adding a seventh interval.
    • Examples: Major 7th, Minor 7th, Dominant 7th, Half-diminished 7th.
  • Chord Progressions: Sequences of chords creating music’s structure.
    • Cadences: Specific sequences providing closure (e.g., authentic, plagal, half cadence).
  • Tuning by Fifths: Circle of Fifths for determining key proximity and modulations.

Scales, Modes, Cadences

  • Building Scales: Starting from fundamental, using intervals (major, minor, exotic scales).
  • Modes: Variations of major and minor scales giving unique tonality (Ionian, Dorian, Phrygian, etc.).
  • Exotic Scales: Acoustic/Lydian dominant, Byzantine, Messiaen’s modes.
  • Borrowing Notes/Chords: From parallel or other modes to add variety.

Rhythms and Time Signatures

  • Tempo: Beats per minute (BPM) setting music’s pace.
  • Note Lengths: Whole note, half note, quarter note, etc.
  • Tuples and Modifiers: Triplets, quintuplets, dotted notes.
  • Time Signatures: Defines bar length (e.g., 4/4, 3/4, 6/8, asymmetric meters like 5/4, 7/8).
    • Polyrhythm: Overlapping different rhythms with common duration.
    • Polymeter: Superposition of time signatures with different bar lengths.

Harmonic Techniques

  • Suspended Chords: Replacing third with second/fourth (e.g., sus2, sus4).
  • Neighbor Tones: Non-chord tones moving stepwise to chord tone.
  • Passing Tones: Notes connecting chord tones via stepwise motion.
  • Escape Tones & Anticipations: Add motion and anticipation.
  • Appoggiatura: Tension by playing non-chord tone on strong beat, resolving stepwise.

Modulations and Complex Harmony

  • Dissonance Utilization: Moving between keys by resolving dissonance.
  • Secondary Dominants: Chords that temporarily tonicize another chord.
  • Circle of Fifths: Tool for finding modulating paths and adjacent keys.

Practice and Application

  • Harmonizing Melodies: Using chords to match melody notes.
  • Extensions and Variations: Adding 7ths, 9ths, borrowing from modes, substitutions for dynamic harmonization.
  • Chord Function and Progression: Establishing home notes, creating tension, and resolving.

Conclusion

Sound and music theory intertwine through fundamental principles of consonance, scales, harmony, and rhythm, allowing diverse musical expressions and innovation.

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