|Relative key||A minor|
|Parallel key||C minor|
|Dominant key||G major|
|C, D, E, F, G, A, B|
C major (or the key of C) is a major scale based on C, consisting of the pitches C, D, E, F, G, A, and B. C major is one of the most common keys used in music. Its key signature has no flats or sharps. Its relative minor is A minor and its parallel minor is C minor.
The C major scale is:
On the piano, the C major scale can be played by playing only the white keys starting on C.
Twenty of Joseph Haydn's 106 symphonies are in C major, making it his second most-used key, second to D major. Of the 134 symphonies mistakenly attributed to Haydn that H. C. Robbins Landon lists in his catalog, 33 are in C major, more than any other key. Before the invention of the valves, Haydn did not write trumpet and timpani parts in his symphonies, except those in C major. Landon writes that it wasn't "until 1774 that Haydn uses trumpets and timpani in a key other than C major... and then only sparingly." Most of Haydn's symphonies in C major are labelled "festive" and are of a primarily celebratory mood. Wilfrid Mellers believed that Mozart's Symphony No. 41, written in 'white' C major, "represented the triumph of light". (See also List of symphonies in C major.)
Many masses and settings of the Te Deum in the Classical era were in C major. Mozart and Haydn wrote most of their masses in C major. Gounod (in a review of Sibelius' Third Symphony) said that "only God composes in C major". Six of his own masses are written in C.
Of Franz Schubert's two symphonies in the key, the first is nicknamed the "Little C major" and the second the "Great C major".
Scott Joplin's "The Entertainer" is written in C major.
Many musicians have pointed out that every musical key conjures up specific feelings. This idea is further explored in a radio program called The Signature Series. American popular songwriter Bob Dylan claimed the key of C major to "be the key of strength, but also the key of regret". Sibelius's Symphony No. 7 is in C major and that key was of great importance in his previous symphonies.
See also: List of symphonies in C major