Since I can’t sing in the higher range anymore, I sometimes drop down an ____.

noun

1. An 8-day period of observances beginning with a festival day
2. A stanza of eight lines ottava rima
3. The first eight lines of an Italian sonnet
4. A musical interval embracing eight diatonic degrees
5. A tone or note at this interval
6. The harmonic combination of two tones an octave apart
7. The whole series of notes, tones, or digitals comprised within this interval and forming the unit of the modern scale
8. An organ stop giving tones an octave above those corresponding to the keys
9. The interval between two frequencies (as in an electromagnetic spectrum) having a ratio of 2 to 1
10. A group of eight

biographical name

1. Octave 1821–1890 French novelist and dramatist