8A
Melody
A coherent succession of pitches.
Scale
A collection of pitches arranged in order from lowest to highest or from highest to lowest. (From the Greek scala meaning ladder.) The chromatic scale divides the octave into 12 equally spaced parts. Most Western scales choose 7 of these pitches and exclude 5. The two primary scales are major and minor; modes, for our purposes, are collections of seven pitches which are different from the major and minor scales, thus sounding, to varying extents, exotic. There are scales which have more than or less than seven pitches.
Octave
A frequency ratio of 2:1. Pitches spaced by one or more octaves have the same name
Arpeggio
A group of notes, associated more with a chord than with a melody, played in succession, often in a regular rhythm and often from low to high or from high to low.
Register
A local domain or subset of the continuum of musical pitch, as in the high register, low register, middle-high register, etc. Tessitura is even more specific; it is the particular range in which an instrument or activity functions most consistently.
Hertz
A measuring unit of frequency expressing vibrations per second. Middle A=440Hz. The (maximal) range of human hearing is 20Hz-20kHz (20,000Hz).
Pulse/Beat
A regular succession of moments which constitute a meaningful temporal context for musical events. Events gain a temporal meaning by their proximity to one of these moments, either by occurring at a moment or between moments.
Harmony
A succession of chords, a chord progression. (Not to be confused with vocal harmony in which one or more singers add a note to a melodic moment or moments creating an interval or chord.)
Pitch
Any point on the continuum of musical pitch. This continuum is analogous to the domain of musically useful frequencies and each point corresponds to some definite frequency within that domain.
Timbre
From the French word for stamp; the sonic character of an instrument from which a listener may identify it.
Functionality
One possible critical model asks the following questions: (1) what are the piece's goals?; (2) did it achieve its goals? A piece may be considered good if the goals are sufficiently ambitious, ethical, etc. and if it achieves these goals. This is a simplistic and problematic model but it is usually the best starting point for apprehending a new piece of music.
Consonance/Dissonance
Terms which refer to musical moments suggesting stability, comfort, and resolution or instability, discomfort, and the need for resolution, respectively. The octave is a very consonant interval; its mathematical ratio is a simple one: 2:1. The major seventh (eleven chromatic steps) is a very dissonant interval; its mathematical ratio is comparatively complex: 45:24.
Syncopation
The accentuation of weak or off-beats.
Style
The choices that a work or performance makes from among the possibilities available.
Instrumentation
The collection of musical instruments that are employed in a given piece. The human voice is an instrument.
Aesthetic
The collection of values which inspire and inform compositional choices.
Interval
The distance between two pitches, often measured in chromatic steps (known also as half-steps); also refers to the sound of two pitches when sounded simultaneously.
Duration
The length, in time, of a piece or section of a piece.
Dynamics
The loudness and softness of a given piece of music.
Texture
The manner in which the musical voices are layered, often to create a sense of thickness or thinness. Monophonic texture suggests one voice identity (which may be doubled, tripled, etc.); homophonic texture suggests multiple voices that do differing things where one stands out in the foreground as most important while others serve in background; polyphonic texture suggests multiple voices that are independent of one another.
Meter
The pattern in which a regular succession of rhythmic pulses is organized. One unit of this pattern is called a bar or measure. The most common meter in Western popular music is 4. Far less frequent but not exotic is 3. 2 may be thought of as half of 4 and 6 may be thought of as twice 3; 5, 7, and 9 are rather exotic meters in Western music.
Rhythm
The pattern of events in time. The pattern is detectable and repeats itself in many kinds of music; a notable exception is a fair amount of 20th century modernism which tends to obfuscate patterns and/or to use them only once.
Ostinato
The repetition of a particular pattern. This function is often served by an instrument in the bass register.
Form
The shape or architecture of a musical composition as defined by its organization of sections or materials. Some common forms include the arch form (ABA), the rondo (ABACADA, etc.), 32-bar song form (AABA), and cyclic forms such as the 12-bar blues
Tempo
The speed of the pulse.
Polyrhythm
The superimposition of different rhythms.
Chord
Three or more pitches sounded simultaneously
Mixed Meter
When the meter changes; the juxtaposition of different meters.