What are scales and where are they used? How are they defined by name?
They're notes in an arrangement which provides melodic value. All the notes sound in key and when put together in different combinations the scale can be used to create music, solos and improvisations.
How scales are named is by what the key is in a song, like Beethoven's 9th Symphony in D major is an example of a d major scale
think of it as a home note.

if we're not making sense to you, you're better off googling for some absolute beginner music theory lessons. no point in us redoing a lesson that is probably done better/more completely by someone else.
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But what does in key mean?

The key is always "home". So, if a song is in the key of Emajor; then when you play the chord Emajor, then it doesn't feel like it needs to go anywhere else. It's already "at home".

Quote by kingking22
They're notes in an arrangement which provides melodic value. All the notes sound in key and when put together in different combinations the scale can be used to create music, solos and improvisations.
Technically, no. If I'm in the key of Emajor, I can play any damn note/chord I want, even notes/chords that aren't considered "diatonic" (in other words: not either made of notes from the key signature [non-diatonc chords]/not notes in the key signature [non-diatonic notes]). The notes played do NOT matter; it's the tonic chord that matters.
Last edited by crazysam23_Atax at Nov 27, 2013,
A scale is an ordered series of notes of notes that follow a particular step pattern. It provides us with a way of "climbing" (ascending or descending) from one note to a specific destination (usually an octave).

The Oxford Dictionary of Music defines Scale:
Scale (from It. scala, `staircase', `ladder'; Ger. Tonleiter; Fr. gamme). A series of single
notes progressing up or down stepwise. Thus, a series of notes within an octave used as the
basisof comp. Scales are arbitrary, and the no. in use throughout the world is incalculable....(continues)

The Harvard Dictionary of Music defines Scale:
Scale [F. gamme; G Skala, Tonleiter; It scala; Sp escala, gama] I. The tonal material of music arranged in an order of rising pitches. Since the tonal material varies greatly in different periods as well as different countries (e.g. China) there are a large number of scales...(continues)

The New Grove Dictionary of Music and Musicians defines Scale:
Scale (Fr. gamme; Ger. Tonleiter; It. gamma). A sequence of notes in ascending or descending order of pitch. As a musicological concept, a scale is a sequence long enough to define unambiguously a mode, tonality, or some special linear construction, and that begins and ends (where appropriate) on the fundamental note of the tonality or mode; a scale, therefore, is usually thought of as having the compass of one or more octaves. The following discussion is limited to the scales of European musical theory...(continues)

Another useful reference book is a book called Music Notation and Terminology by Karl Gehrkins.
In his book Gehrkins defines scale:

A scale (from scala, a Latin word meaning ladder; Ger. Ton-leiter) is an ascending or descending series of tones, progressing according to some definite system, and all bearing (in the case of tonality scales at least) a very intimate relation to the first tone—the key-tone or tonic.


He goes on to distinguish scale and key:

Quote by Karl Gehrkins, Music Notation and Terminology
A key is a number of tones grouping themselves naturally (both melodically and harmonically) about a central tone—the key tone. The word tonality is often used synonymously with key in this sense.

The difference between key and scale is therefore this, that while both key and scale employ the same tone material, by key we mean the material in general, without any particular order or arrangement in mind, while by scale we mean the same tones, but now arranged into a regular ascending or descending series. It should be noted in this connection also that not all scales present an equally good opportunity of having their tones used as a basis for tonality or key-feeling: neither the chromatic nor the whole-step scale possess the necessary characteristics for being used as tonality scales in the same sense that our major and minor scales are so used.

The Harvard Dictionary of Music also specifically points out the distinction between scale and key when defining key:

Key (2) By specialization, the term came to mean the "main" key of a composition, i.e. the main note or "tonal center" to which all its notes are related and finally, by extension, the meaning of the entire tonal material itself in relation to its center. Thus, "key" is practically synonymous with tonality. There is, however, a distinct difference between key and scale, since numerous notes extraneous to the scale can be used in the key, e.g. as chromatic variants or in connection with modulation.