Who was Christina Aguilera's vocal coach that Lady Gaga went to as well?

Christina Aguilera's vocal coach, who also worked with Lady Gaga, is Etta James' former vocal instructor, the renowned coach and vocal producer, Mimi Arnold. She is known for her expertise in vocal technique and has helped many artists refine their singing skills. Both Aguilera and Gaga have credited her for enhancing their vocal performances.