Piano notes
When discussing Angelina's vocal range or individual notes she has sung, people often refer to the notes on a piano using so-called scientific pitch notation↗. On a standard 88-key piano keyboard, the notes range from a low of A0 (at a frequency of 27.5 Hz↗) on the left to a high of C8 (at just over 4186 Hz) on the right. In the image above, the blue key is so-called middle C↗ (at approximately 261.6 Hz). The yellow key is known as A440↗ (at exactly 440 Hz) which serves as the basis for the most common modern piano tuning↗.
The non-numeric part of the notation is the name of a musical note↗, from A to G, with possible sharps↗ (♯) and flats↗ (♭) on most of those notes. The subscripted number in the notation refers to which octave the note is in. Despite the fact that the leftmost key is an A, each octave starts on a C key (C1 corresponds to the third white key from the left—the second white key from the left is B0, not B1).
In each octave, there are 7 white keys corresponding to the notes C, D, E, F, G, A, and B, and 5 black keys corresponding to (depending on the key↗ one is playing in) C♯ or D♭, D♯ or E♭, F♯ or G♭, G♯ or A♭, and A♯ or B♭. Thus there are a total of 12 keys per octave, each of which differ by what is called a semitone↗. Each higher octave is pitched at twice the frequency of the previous one—so, for example, the frequency of C2 (65.4064 Hz) is twice that of C1 (32.7032 Hz).
The frequencies stated here are for an idealized piano with standard equal temperament↗ tuning and differ slightly from real-world pianos tuned in that way. See the various Wikipedia articles, especially the one linked to in the box above, for more details about all of this.
References
There are no individual references. All of the information here is based on the various Wikipedia articles linked to above.
