German musician Anna-Maria Hefele plays a number of instruments, including piano, mandolin, and harp. She is also an accomplished instrument builder, making her own didgeridoo, wooden alpine flute, and ocarina.
However, she is perhaps best known as a virtuoso overtone singer, and has studied and practiced the technique extensively since 2005. For those who don't know what overtone singing is, here is Hefele's explanation from her YouTube channel:
"Overtone singing is a voice technique where it seems like one person sings two notes at the same time. You can sing the overtone scale on one fundamental. Another fundamental has its own overtone scale, so in order to have more overtones to sing nice melodies, you can use different fundamentals and change them while singing."
Her most famous video (which went viral with over 10 million views) features a stunning demonstration of polyphonic overtone singing:
Recently, doctors at the University Medical Center Freiburg, Institute for Musician's Medicine created a recording of Hefele singing in an MRI machine, making it possible to see all parts of the vocal tract, and how they work together to make overtone singing possible. Here is that recording, featuring Hefele singing Mozart's "Sehnsucht nach dem Frühlinge."