Question about music notes- black x?

Question:

Question about music notes- black x?

I have a question about a symbol in my music. I have play the alto saxophone. I have a #G followed by an #F in the key signature, but in the front of the F is a black X. What does this mean?

Best Answer - Chosen by Asker: An X preceding a note means it's a double-sharp. They're used frequently when a measure is filled to capacity with other notes, often found in classical and Flamenco music.

The X in front of the F note means it is a G note.

The double flat is shown as bb and used in the similar way as a double -sharp.

Sometimes, you will find Xs or bbs in a key signature, but rarely done.