An Em7 is based on the notes: E (root) G (minor third) B (the fifth) D (the seventh)
The same as an A minor chord: A, C, E. If the seventh were included, G#.
The notes of the G Major chord are G, B and D.
The first, third, fifth, and seventh note derived from the C major scale, so: C-E-G-B for a major seventh chord (Cmaj7) and the seventh note flattened to Bb or B flat in the C7 chord commonly used in pop/blues as a final chord but in most Classical Music to be resolved in F.
G B and D
G, b, d
The first, third, fifth, and seventh note derived from the C major scale, so: C-E-G-B for a major seventh chord (Cmaj7) and the seventh note flattened to Bb or B flat in the C7 chord commonly used in pop/blues as a final chord but in most classical music to be resolved in F.
It means the dominant seventh chord. In C major this would comprise of the notes G B D and the seventh F
All positions would have the same "relative" number of notes. All notes depend on the player, not the instrument, but one should be able to play 20 or more per position.
B flat, D, F, A flat
G, Bb, D, F
The E-major triad is composed of an E, a G#, and a B. To make this chord minor, flat the G#.