C#maj7 – Do# Maj Seventh
In music theory, C# maj seventh chord is built on C#-E#-G#-B# formation: root-major third-minor third-major third. Basic maj seventh chord has a formation C#-G#-B#-E#-G# from basses to trebles in the guitar.
This chord is derived from a seventh chord. In Music theory, seventh chords are built by four different notes and chords seventh function is a minor seventh interval. But in Maj seventh chords, seventh function is a major seventh interval. So, it is a different kind of seventh chord than dominant seventh chord type.
In Guitar, generally maj seventh chords are expanded by same kind notes that repeat themselves in different octaves. Maj seventh chords are built by a harmonic interval order such as: root-major third-minor third-major third(C-E-G-B). Though it was used also in classical music, these chords are mainly used in contemporary forms like jazz etc nowadays.