What is what key is oboe in?

The oboe is a transposing instrument, which means that music written for the oboe is written in a different key than it sounds. The oboe is typically written in concert pitch, which is the key that the music actually sounds in, and then transposed up a whole step to sound two semitones higher. For example, if a piece of music is written in C major for the oboe, the oboe will actually play it in D major. So, if the oboe plays a C note, it will actually sound like a D note. Therefore, to play in the same key as other instruments, oboe players must learn to read music in a different key signature than concert pitch.