piano chord
Badd9
B1D♯3F♯5C♯9
A major triad with a ninth added and no seventh — which is what tells it apart from a ninth chord.
What is true of it
Badd9 is B, D♯, F♯ and C♯ — 1, 3, 5 and 9 counted from B.
On an instrument that cannot reach all 4, the 5 goes first, in that order.