¿Existe alguna nota más baja que C1?

That's right! In Scientific Pitch Notation (SPN), the octave numbers change specifically on the note C.

Here is a quick breakdown of how it works at the bottom end of the piano keyboard:

• Sub-contra octave: Notes like A0 and B0 sit right below the first C on a standard 88-key piano. Because they fall below C1, they are given a 0 instead of a 1.

• The Turn of the Octave: The very next note up is C1, which officially starts the contra octave.

• Going Lower: On a standard piano, A0 is actually the lowest key on the keyboard (with a frequency of about 27.5 Hz). Anything below A0 (though rare on standard acoustic instruments) would theoretically move into negative numbers, like Ab-1 or G-1, though you rarely encounter music written down there!

Is there a specific piece you're looking at, or a note range you're trying to figure out?