Forum: music.stackexchange.com
Tags: <guitar><chords><jazz>
Title: Does C° also indicate a major seventh chord?
Question: I had always thought that this notation indicated a major seventh chord: [C°]. At least it seemed to make sense that way in some of the chord sheets I have used in the past.  I am now finding that it more commonly seems to represent a diminished chord, as in [Ab°(b13)] or [A flat dim flat 13]. My first question is has anyone here ever seen [°] used to represent a major seventh, or am I labouring under an illusion ;-)

Answers:
sents: text: Never.
text: C° is always C diminished.
text: C major seventh can be signed with a triangle after the C. Bear in mind that half-diminished is signified by a circle with a diagonal line through it.
text: Cmaj7 is C E G B. C°7 is C E&flat;
text: G&flat; B&flat;&flat;. C half dim.
text: is C E&flat;
text: G&flat; B&flat;.
text: Note: they all contain C E G B something .
answer_details: author: music.stackexchange.com/users/2808/Tim
score: 15
sents: text: I have never ever seen "o" denoting a major 7 chord.
text: A triangle can be used for maj7 in some books (e.g. the Aebersold play alongs), and 'o' is always diminished.
text: You may also encounter a slashed cirle (ø) for half diminished (min7 b5) chords.
answer_details: author: music.stackexchange.com/users/1079/gurney alex
score: 6
sents: text: If you're playing from sheet music that's been handwritten, or perhaps photocopied multiple times, it's not uncommon for the small △ symbol, which denotes Maj7 to end up looking like small circle °, which, as you say, denotes Diminished.
text: Or if the copyist isn't particularly careful, the circle and triangle can end up looking similar.
answer_details: author: music.stackexchange.com/users/9426/Brian THOMAS
score: 5
sents: text: o a degree sign for diminished triad or o7 for diminished seventh chords.
text: ø7 for half-diminished seventh chords. Δ7 a delta or triangle for major seventh chords.
text: Other signs are used capital M for major or lower case m for minor, etc.
text: You may have been mistaking the delta for a diminished sign.
answer_details: author: music.stackexchange.com/users/23919/Michael Curtis
score: 5
sents: text: I had always thought that this notation indicated a major seventh chord: [C°].
text: At least it seemed to make sense that way in some of the chord sheets I have used in the past.
text: This must have been an error.
text: As Cmaj7 is a static chord (or eventuell would lead to F)
text: it couldn't be substituted by C°, while latter might have a dominant function to Db, (or E, G and Bb) and certainly can't be replaced by Cmaj7.
text: Edit: As the other answers confirm C°7 was never meaning C major 7 .
text: ` I've edited the last words ...
text: was never a major 7 as someone could understand A-major 7 ( a was meant as article not as chord).
answer_details: author: music.stackexchange.com/users/56219/Albrecht Hügli
score: 2
sents: text: While answers are correct that C° means C diminished and CΔ means CMaj7, there is more to the story here.
text: In jazz, C° is a very common delayed resolution to CMaj7.
text: For example, in a simple ii-V-I: | Dmin | G7 | CMaj7 | CMaj7 |
text: it's very common to hear pianists harmonize this with:
text: | Dmin | G7 |
text: C°7 CMaj7 | CMaj7 |
text: In this context, the scale typically used over C°7 is C whole-half (enharmonically, C D E♭ F G♭ A
text: ♭ A♮ B ).
text: This diminished scale contains the BMaj triad, which resolves up a half step to a CMaj triad when we reach the CMaj7 chord.
text: However, while the C°7 can be voiced with a BMaj triad, this isn't necessarily and isn't always done in jazz.
text: We can simply voice the C°7 chord in its typical fashion.
text: This isn't all that different from a common-tone diminished 7th chord , which resolves ii o7 to IMaj (for example, D♯ o7 to CMaj).
text: After all, D♯ o7 has the same notes as C o7 .
text: But in a jazz context, the bass is often still playing the I, establishing the progress
text: as i o7 - IMaj7.
text: Lead sheets may show this i o7 chord written into the bar, or they may show it above the bar in parentheses to indicate that it's a possible chord substitution.
text: Or, it may not be shown at all, in which case the musician(s) are choosing to add this substitution into the music on the fly.
answer_details: author: music.stackexchange.com/users/40842/jdjazz
score: 0

Summary of the answers:
 C° is always C diminished. C major seventh can be signed with a triangle after the C.You may also encounter a slashed cirle (ø) for half diminished (min7 b5) chords. If you're playing from sheet music that's been handwritten, or perhaps photocopied multiple times, it's not uncommon for the small △ symbol, which denotes Maj7 to end up looking like small circle °, which, as you say, denotes Diminished.  
C° is always C diminished