piano scale
B major
B1C♯2D♯3E4F♯5G♯6A♯7
The seven-note scale everything else is measured against: two whole steps, a half, three whole steps, a half.
Written out
Every accidental is written in, rather than left to a key signature, so the letters can be read one at a time.
The step pattern
BWC♯WD♯HEWF♯WG♯WA♯HB
What is true of it
B major is B, C♯, D♯, E, F♯, G♯ and A♯, and back to B.
Its steps are W – W – H – W – W – W – H, where W is a whole step and H a half.
On the same tonic, B melodic minor differs from it by exactly one note.
Chords made only of these notes
C♯mminorC♯m7minor seventhD♯mminorD♯m7minor seventhEmajorEmaj7major seventhF♯majorF♯7dominant seventh
Found by testing every chord in the catalogue against these 7 sounds, not chosen.