The key signature indicates which notes are sharp, natural, or flat. Every key has a specific signature.
D major has a key signature of F sharp and C sharp D minor has a key signature of B flat
Key signatures are the sharps or flats at the beginning of the staff. To identify the key signature of a scale that consists of all sharps, look at the last sharp in the key signature. Whichever note the last sharp lies on, the key of the scale is one note above it. To identify the key signature of a scale that consists of all flats, look at the note directly before the last flat in the key signature. The second-to-last note is the name of the key signature of flat keys. However, you cannot use this helpful trick with the F Major Scale which only has one flat (B flat).
There is not three notes in any scale or key, if you are asking about the accidentals, there is one flat (Bb) in the key signature plus an additional C sharp for the harmonic minor scale.
A major scale and its relative minor scale share the same key signature.
A Dorian key signature is an earlier style of key signature used on pieces in minor keys. A good example is J.S. Bach's Toccata and Fugue in D Minor, BWV 538, that was notated with a key signature of zero flats rather than the one flat of a contemporary key signature notation for D Minor. The Dorian mode is a mode of the major scale built off of the second scale degree of a major scale and, therefore, a Dorian key signature for D Minor would be the signature for the major scale a whole step below: C Major...therefore zero flats. The D Dorian scale is spelled D, E, F, G, A, B, C and therefore shares the same key signature as C Major in this older notational system. It is now customary within the western tonal system to relate minor keys to the key signature of the major key found a minor third above. D Minor is now written with one flat, the key signature of F Major. Today the "natural minor" scale or Aeolian mode (the mode built off the 6th scale degree of major) is the common reference point for a minor key's key signature.
The scale with four sharps in its key signature is the E major scale.
The scale that has two flats in its key signature is the key of Bb major.
The scale with 2 flats in its key signature is the key of Bb major.
The scale with two sharps in the key signature is called the D major scale.
The key signature of a musical scale with two flats is Bb major.
The key signature for a harmonic minor scale typically has raised seventh note compared to the natural minor scale.
The key signature of the harmonic minor scale typically has raised seventh note compared to the natural minor scale.
3/4 is a time signature, not a key signature.
The key signature of the C minor scale has three flats: B flat, E flat, and A flat.
D major has a key signature of F sharp and C sharp D minor has a key signature of B flat
Key signatures are the sharps or flats at the beginning of the staff. To identify the key signature of a scale that consists of all sharps, look at the last sharp in the key signature. Whichever note the last sharp lies on, the key of the scale is one note above it. To identify the key signature of a scale that consists of all flats, look at the note directly before the last flat in the key signature. The second-to-last note is the name of the key signature of flat keys. However, you cannot use this helpful trick with the F Major Scale which only has one flat (B flat).
The key signature with one flat is either F major or D minor.