MusicXML 4.1 Draft
MusicXML 4.1 Draft > MusicXML Reference > Examples > <key-octave>

<key-octave>

key-octave-element

<key>
   <key-step>F</key-step>
   <key-alter>1</key-alter>
   <key-step>G</key-step>
   <key-alter>1</key-alter>
   <key-octave number="1">4</key-octave>
   <key-octave number="2">4</key-octave>
</key>