What is the minor key that has 4 sharps?

The minor key that contains 4 sharps is C# minor. This key signature is derived from its relative major, E major, which has 4 sharps as well. In the context of music theory, the sharp notes in the key of C# minor are C#, D#, E, F#, G, A, and B.

Understanding key signatures is vital for recognizing the relationship between major and minor keys, as well as for reading and writing music accurately. In this instance, C# minor stands out because its sharp count directly corresponds with the established key signature rules. The identification of this key is crucial for musicians as it informs them about the scale degrees, harmonic structures, and potential modulations that can occur within the context of C# minor.