C Major 7th
maj7
0 - 4 - 7 - 11Major + major 7th
About C Major 7th
C major seventh is the chord that sounds like a held breath. Add one note to a plain C major — the B just below the root — and the chord stops being a place to arrive and becomes a place to linger. It is the sound of soft jazz, of bossa nova, and of almost every advert that wants to feel calm.
The note that changes everything
C, E, G, B — the major triad plus a major seventh. That B sits a semitone below the C above it, and the ear hears the tension of that half step without hearing it as a problem, because the note also belongs to the key. Nothing needs to resolve, so the chord can sit still.
Change the B to B♭ and you get C7, which does need to resolve — to F, urgently. The difference between Cmaj7 and C7 is one fret and two completely different jobs.
Voicings that work on guitar
The open shape is a C major with the first finger lifted from the B string, leaving it open. It is the easiest maj7 on the instrument, and it rings.
The barre-free shape on the middle strings — root on the A string at the third fret, then 5–4–5 — is what jazz players reach for, because it leaves the low strings free for a bass line and drops neatly into Dm7 and G7.
Where it shows up
As the I chord in C major and the IV in G major. In jazz it opens the ii–V–I: Dm7 to G7 to Cmaj7, the most common cadence in the repertoire, and the reason this chord is usually the first seventh a guitarist learns after the dominant.
In pop it is used for stillness rather than motion — an intro, an outro, a verse that stays on one chord. A song that ends on Cmaj7 instead of C ends softly and slightly unresolved, which is often exactly the point.