Audition: the action, power, or faculty of hearing. (Oxford). The technical term for the sense of hearing. (Hockenbury, 96) Processes the signals sent to the brain from our ears. (Doidge, 48) Converts the physical properties of “sound-wave energy” into “electrochemical”  “neural” activity that (enables the) “perception” of sound. (Kolb, 313)

Humans are capable of responding to a wide range of “sounds,” from faint to blaring, simple to complex, and harmonious to discordant. (Brooker, 96) A youthful ear can hear ten octaves of sound, spanning a range from about thirty to twelve thousand vibrations a second. The average ear can distinguish sounds a seventeenth of a tone apart. From top to bottom, we hear about fourteen hundred discriminable tones. (Sacks, 132) Also referred to as ‘auditory system.’

Every culture has songs and rhymes to help children learning the alphabet, numbers, and other lists. Even as adults, we are limited in our ability to memorize series or to hold them in mind unless we use “mnemonic” devices or patterns - and the most powerful of these devices are rhyme, meter, and song.
— Oliver Sacks, Musicophilia

Auditory Processes: (include) perceiving sound, detecting “loudness,” detecting location, detecting patterns in sound, processing “language,” and processing “music.” (Kolb, 306)

Music: organized sound. The basic element of any sound are loudness,  "pitch," "contour," "rhythm," "tempo," "timbre," spatial location, and "reverberation." When we listen to music, we are actually perceiving multiple attributes or dimensions. (Levitin, 14) The simplest type of music involves a single voice singing a series of intervals, one after the other, to produce a melody. (Powell, 102) Mathematicians have studied the patterns in music for thousands of years. They have found that geometry can describe chords, rhythms, scales, octave shifts, and other musical features. (Grandin, 143) The “corpus callosum,” the great “commissure” that connects the two hemispheres of the brain, is enlarged in professional musicians and a part of the auditory cortex has an asymmetric enlargement in musicians with absolute pitch. (Sacks, 95)

Key: a system of notes definitely related to each other, based on a particular note, and predominating in a piece of music. (Oxford) Has to do with a hierarchy of importance that exists between "tones" in a musical piece. The 'tonal context' of a piece of music. A tonal center in a central set of pitches. The key can change during the course of a song, but it is generally something that holds for a relatively long period of time, typically on the order of minutes. (Levitin, 70) One of the ways a composer can keep up the interest level of his listeners is to change key. A song or any other piece of music is divided up into 'phrases' and the 'key note' will often be the final one of a phrase. (Powell, 163)

Melody: the main theme of a musical piece. (Levitin, 16) Every melody is made up of a string of notes of different “pitches.” (Powell, 7) The embedding of words, skills, or sequences in melody and meter is uniquely human. The usefulness of such an ability to recall large amounts of information, especially in a preliterate culture, is surely one reason why musical abilities have flourished in our species. (Sacks, 239)

Contour: a particular level, or a sequence of varying levels of pitch, tone, or stress. (Oxford) Describes the overall shape of a melody, taking into account only the pattern of 'up' and 'down' (of a tone), not the amount by which it goes up or down. (Levitin, 15)

Octave: an interval embracing eight notes on the diatonic scale, the highest note having twice the frequency of, and the same alphabetical name as, the lowest. (Oxford) When we double or halve a "frequency," we end up with a note that sounds remarkably similar to the one we started out with. This relationship, a frequency ratio of 2:1 or 1:2, is called the "octave." (Levitin, 29)

Pitch: the relative highness or lowness of a sound, determined by the frequency of a sound wave. (Hockenbury, 97) A purely psychological construct related both to the actual frequency of a particular tone and to its relative position in the musical scale. (Levitin, 15) Pitch is one of the primary means by which musical "emotion" is conveyed. (Levitin, 25) Music composed in major keys sounds more self-confident and generally happier than music composed in minor keys. (Powell, 142) The auditory cortex has a ‘tonotopic' map, with low to high tones stretched out across the cortical surface. In this sense, the brain contains a ‘map’ of different pitches, and different areas of the brain respond to different pitches. Pitch is so important that the brain represents it directly; unlike almost any other musical attribute. (Levitin, 27) 

Reverberation: refers to the perception of how distant the source is from us in combination with how large a room is. (Levitin, 15) Clapping your hands … in a small room full of furniture and heavy curtains, the sound dies away almost immediately and the room is said to be acoustically ‘dead.’ In a large room with hard walls, the sound bounces back and forth off the walls several times before the sound dies away and the room is described as ‘lively.’ In a concert hall, it might take as long as a couple of seconds for this reverberation to die away. Musicians sound better in a ‘live’ room than a ‘dead’ one. (Powell, 231) Also referred to as ‘reverb.’

Echo: a repetition of a sound or sounds due to the reflection of the sound waves. (Oxford) Our brains can estimate the size of an enclosed space on the basis of the reverberation and echo present in the signal that hits our ears. (Levitin, 106) Although we enjoy the effect of sounds lasting longer because they are bouncing around the room, we want all the bounced sound from each note to overlap so that it reaches our ears as a single, long note. If the walls of the room are  a long way away, the time between bounces will be too long and we won’t hear a single, extended note. We will hear the note, then a gap, then the note again - the dreaded ‘echo.’ Concert hall designers live in the hope that their designs will give the audience lots of pleasant reverberation, but no echoes. (Powell, 231)

Rhythm: refers to the duration of a series of notes, and the way that they group together into units. (Levitin, 15) Any piece of music consists of a stream of sounds spread over a certain amount of time, and we use the word rhythm to describe how we organize the timing and emphasis of those sounds. (Powell, 182) Listening to “music” is not just “auditory” and “emotional,” it is “motoric” as well. “We listen with our muscles,” as Nietzche wrote. We keep time to music, involuntarily, even if we are not consciously attending to it, and our faces and postures mirror the ‘narrative’ of the melody, and the thoughts and feelings it provokes. (Sacks, xi)

Scale: a series of notes ascending or descending by fixed intervals, especially one beginning on a certain note; specifically any of the graduated series of notes into which an octave is divided. (Oxford) A subset of the theoretically infinite number of pitches. Every culture selects these based on historical tradition or somewhat arbitrarily. The specific pitches chosen are then ‘anointed’ as being part of that musical system. The names “A,”  “B,”  “C,” and so on are arbitrary labels that we associate with particular frequencies. In Western music, most instruments are designed to play these pitches and not others. The trombone and cello are an exception, because they can slide between notes. (Levitin, 27)

Diatonic: using only the notes proper to one key… Based on a scale with five tones and two separated semi-tones. (Oxford)

Tempo: overall speed or pace of (a musical) piece. (Levitin, 15) Relative speed or rate of movement; pace; time; the speed at which music should be played. Origin from Latin ‘tempus’ - time. (Oxford) The tempo of a piece of music is its pulse rate - how often you would tap your foot to it. (Powell 182) 

Timbre: a kind of tonal color that is produced in part by 'overtones' from (an) instrument's vibrations. Distinguishes one instrument from another. (Levitin, 15) The distinctive quality of a sound that enables us to distinguish easily between the same note played on a saxophone and on a piano. Most of the sounds we experience do not consist of a single frequency but are ‘complex,’ consisting of several sound-wave frequencies. This combination of frequencies produces the timbre of a sound. Every human voice has its own distinctive timbre, which is why you can immediately identify a friend’s voice on the telephone from just a few words, even if you have not talked to each other for years. (Brooker, 97) The distinctive quality of a sound, determined by the complexity of the sound wave. (Hockenbury, 96)

Tone: any of the large intervals between successive notes of a 'diatonic' scale. (Oxford) A discrete musical sound. Refers to what you hear. 'Note' refers to what you see written on a musical score. (Levitin, 14-15)