I am a Tabla (a North Indian percussion instrument) player and I am trying to learn the western music theory. My study was going well until I stumbled upon keys and scales. Now though I know what scales are. They are just a bunch of notes the composer decided to use in his music. But the problem is that sometimes the word 'scales' is interchangeably used with 'keys'. So I searched about keys and haven't found much about them except the same fact that people sometimes use 'keys' instead of 'scales'. Though I know what 'Key Signatures' are. Also I heard about "playing different scale but staying in the same key". So from that sentence and other research I am pretty sure keys and scales are different. But how are they different? Does key mean key signature? Or are key signatures part of key? And what's the difference between keys and scales?

I've recently learned about modes hoping that it would clarify my doubt but it didn't. I want an answer which has a perfect base such that I can go further study music theory without ever doubting about keys and scales again.

6 Answers 6


[A scale is] just a bunch of notes the composer decided to use in his music.

This is correct, or at least it's a valid way to look at it. In western music, the key chosen for a piece implies both a scale and a tonal center, but alternate scales may be used without changing key, and in some ways and some forms of music, the tonal center may also change without it being considered a change of key.

If someone tells you a piece is in the key of A minor, then you can assume you will use the A minor scale for least the beginning, end, and a good portion of the piece. It won't always be just like that, but it's the best assumption. There may be some use of the A harmonic minor scale and/or the A natural minor scale in western music without changing the key of the piece, which can still be in A minor.

To be clear, in Western music it is not uncommon to use multiple scales in a single piece, even if that piece stays in the same key the entire time. In Western classical music, it is very common for a piece to have more than one key, with one or more scale being used in each key. In general, the number of scales used in a piece is equal to or greater than the number of keys used.

So, each key comes with one scale attached to it, with other scales that go along with that key being optional.

A mode is a special kind of scale. You can think of a mode as just being a scale, and we just use the word "mode" for some scales and "scale" for others. Confusingly, some patterns of notes have two different names, one "scale" name and one "mode" name. As you work to understand scales and keys, it's all right to consider "mode" to be another word for "scale". As you understand more, you'll see why there is a separate word for it, but at the beginning just consider them to be the same thing.


You determination that keys and scales are not the same is correct. They are not the same but in general - most scales are based on a particular key. Let me try to explain keys and scales in simple terms without getting into a great deal of music theory.

Keys determine the group of notes that the composer has to choose from when composing the music. In Western Music there are twelve notes that exist between octaves. They are A (A#/Bb) B C (C#/Db) D (D#/Eb) E F (F#/Gb) G (G#/Ab). The letters in the parenthesis are the same note in practical application because they are played by the same key on piano or same string/fret combination on guitar and in the same place on all instruments that have a fixed tuning system. So there are keys on the piano which would play a note which would be referred to as either an A sharp (A#) or B flat (Bb) - depending on which key you are in.

Of the twelve notes, only seven exist in each key. A key can be major or minor. The key signature tells which notes on the musical staff are to be considered (and played) sharp or flat. The key of C major has no sharps or flats thus the key signature shows no sharps or flats. The seven notes in the key of C major are C D E F G A and B.

A scale is an ascending series of notes (each one higher than the preceding note) that span an octave. Scales are typically based on a key. So the C major scale would consist of the the notes C D E F G A and B. So to play a C major scale on an instrument, you would start on C and play C D E F G A and B and end the scale by playing C one octave higher.

The following types of scales contain 7 notes each: Major, Natural Minor, Harmonic Minor, and Melodic Minor. The pattern of intervals between notes (either whole or half step/semitone) is what determines the type scale. These seven note scales are called diatonic scales.

In a major diatonic (7 note) scale the pattern of intervals is whole whole half whole whole whole half. Whole is two semitones and half is one.

So there is one full (whole) step between the first two notes of a diatonic major scale and one full step between the 2nd and 3rd notes but only a half step between the 3rd and 4th notes. In a natural minor scale the intervals are whole half whole whole half whole whole.

Scales can also consist of 5 notes. 5 note scales are known as pentatonic scales and also span an octave. But to span an octave with only 5 notes, larger steps or gaps between notes are required. Just as with diatonic scales, there are different types of pentatonic scales (ie major and minor) and again the pattern of intervals between notes is determined by the type scale (or you could say the pattern is what determines the scale type).

Other variations of scales can be invented by the musician to add a particular flavor to their music.

In summary, scales are played in ascending note order and are usually based on a particular key (with the exception of the chromatic scale which is all twelve possible notes played in ascending order). The key determines which notes are available to choose from for a particular scale. In general, scales will contain notes derived from the key it is based on. So a major diatonic scale will contain the same notes as the key it is derived from. C major scale shown above contains all the notes in the key of C major - played in ascending order.

A major pentatonic scale would also use notes from within the key it is derived from - but only 5 of the seven notes would be used.

Think of a scale as climbing or scaling a ladder. The key and type of scale determines how far apart the steps on the ladder are from one another. Pentatonic, or diatonic determined how many steps on the ladder. Each ladder is the same height (an octave) but the spacing for a 5 step ladder is going to be different that for a 7 step ladder.

Hope that helps.

  • If I'm not wrong, melodic minor is heptatonic, but not diatonic.
    – 021
    Oct 2, 2019 at 15:03

A very simplistic way to look at it is this:

A scale is a defined set of ordered pitches.

A key is the use of a scale in actual music.

To say that a piece is in the Key of A, would mean that usually most of the notes in the piece would follow the tonal rules of the A Major scale.

In Indian music there are two styles that I am aware of, Carnatic and Hindustani. I have forgotten which is which, but in one of them the scale is set in unique ways for each piece where a unique scale is associated with a single raga. This is a different approach than the "western" tradition where (by comparison) there is a limited set of predefined scales that are used in almost every piece.


In the Common Practice Period (CPP) descriptions of Western Harmony (still used in much if not most music, Latin, pop, jazz, movie themes, country, rock, blues, etc.) a "key" consists of a primary note (termed the "tonic") and a set of chords commonly used to highlight this note (and its chords). A scale is a set of notes with linear order. In common practice, there is a primary scale associated with each key or vice versa (the theory is derived from the music; the theory is descriptive and is supposed to explain the way the music has been constructed.)

In CPP harmony, there are two common types of keys by pattern. Each key may be moved to another pitch. There are major keys with a major scale which is 8 notes with a particular pattern. A scale repeats at an "octave" (the historical name for a tone at double the frequency of another note). In (for example) the key of C-major the notes are C-D-E-F-G-A-B-C (the second C is double the frequency of the first.) The spacing in terms of half steps (approximately 18/17) and whole steps which are two half steps is W-W-H-W-W-W-H. I'm using C-major for notational convenience.

There are chords associated with C-major. The "tonic" chord is C-E-G. This is the "home" chord and composers write music which sets up the expectation that this chord will be used to end a piece (or section thereof). There are many chords with different usage (or function) associated with the key of C-major. For example, the "dominant" chord in C-major is G-B-D often with a fourth note G-B-D-F added. The "feeling" (I don't know a good word for "auditory feeling") of being in C-major is most often indicated by music with chords F-major (F-A-C) followed by G-major followed by C-major. There's much more. There are minor chords like a D-minor chord D-F-A (the pattern is slightly different from a major chord) and some pieces can end with D-minor followed by G-major followed by C-major.

A minor key has a minor chord as its home chord. Minor keys are quite a bit more complex than major keys. The scale associated with a minor key (I'll use A-minor for notational convenience) is A-B-C-D-E-F-G-A which is a circular permutation of the C-major scale. However, there is another and more important difference. Scale steps 6 and 7 (notes F and G here) are mutable. Each may occur with two different notes. (Lowering a note is signaled by an appended b and raised by an appended # called "flat" and "sharp" respectively.) In A major, the notes F and G may be replaced by F# or G#. There are a bunch of common patterns that are described in various books.

There's much more, especially in the idea of writing for simultaneous melodies that sound good both individually or together (counterpoint). There are also structural conventions for various types of pieces. It's big.

For more (and better I'd guess), check out various websites that do harmony. There are some good (if old because of copyright restrictions) books available. I like Frank Shephard's book on harmony as well as Francis York's books on harmony and counterpoint. They are old but serviceable and free.

"Music Theory for Ordinary People" and "Open Music Theory" are two good websites. There are lots of others.


A key usually refers to a collection of 7 notes that have a hierarchical ordering and specific functions; for example, the most important note in any key is the "tonic", which is the note where most pieces end, and gives the listener the feeling of repose. Other important notes in any key are the dominant and subdominant. Keys also have an implied harmonic structure - they allow for building chords (basically 2, 3 or more notes, played together). The chords are also called "tonic" or "dominant" etc depending on the "root" note that is used to build the chord; thus you have the tonic chord and the dominant chord, which are the most important of any key.

Another important concept is "mode", which effectively modifies some of the notes in the key by raising or lowering them. For example, a C major key contains notes CDEFGAB, while a C minor CDEbFGAbBb

A scale is basically an ordering of notes by steps, starting and ending with the tonic, going up or down. Thus, in the key of G major (which contains an F#), the G major scale is GABCDEF#G.

Scales are usually technical exercises intended to be played or sung. A key is more of an abstract concept (it's the "raw material" to write a tune, or to build a scale).

You CAN play different scales with the same key signature. But that's a different question that would be too long to answer here.

  • So what if I want to make my own music? How would I use both the things? Oct 29, 2015 at 19:07
  • Composers usually pick a key to write a song, and use the chords commonly present in that key. Scales are more of a technical exercise - they are used to develop accuracy and fluency when playing an instrument or singing. Since scales are basically an arrangment of all the notes of a key, playing scales also "educates" the ear of the student to hear and recognize the key, and to improvise melodies using the correct notes of the key.
    – Alejandro
    Oct 29, 2015 at 19:23

Key (location in sound) - Root Note

Mode (flavor or color) - Set of notes or interval pattern stacked on top of the root noted.

You can play Key of "C (Major)" (all white keys) without sharps or flats (black keys). But you're simultaneously kinda playing 7 modes (flavors).

All white keys!!!!!!!!!!

C to C is Major

A to A is minor

B to B is locrian

D to D is dorian

E to E is phrygian

F to F is lydian

G to G is mixolydian

.... they are all key of C. The interval jumping is taken care of by the skipped black keys.

So, for example, you want to play minor in any key. Look at the white keys from A to A and you get 2122122. Start on any white or black key and play that interval going to the right and you are in minor in the "key" that you started on.

Obvious follow up question: "Can you play black notes and still be in key of C?" Yes. Most definitely. Take Phrygian Dominant (1312122) and cycle it to get all 7 relative scales (jazz). Root any of them on C and you are in "Key of C." Depending on the mode, it might be easier to write it in a different key to be less cluttered. That's all.

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