I've been looking around the internet for this. Surprisingly, I can't understand exactly what pitch spelling is. I know what a pitch in the musical sense means, but I can't understand what do we do exactly when we pitch-spell?
Spelling a pitch relates to the system of naming notes by letters (A-G) and sharp(#) and flat (♭) signs - and sometimes double sharp and flat signs, resulting in names or 'spellings' like 'A♭', 'D#', 'F♭♭'.
Translating between frequencies in Hz and such names is non-trivial. You need to consider :
- The 'concert pitch' you are taking as a reference
- The temperament in which the piece is played
- The overall key that the music would be notated in
- Use of the correct enharmonic equivalents for accidentals (Using the correct enharmonic equivalent, Purpose of double-sharps and double-flats?)
If translating between, say, MIDI note numbers and 'spelled' names, the first two steps can be skipped.
Spelled pitch names often have an octave number appended for disambiguation - e.g. 'A♭3', 'D#5'.