Identify the tonal center:
- Play or listen to the song multiple times to familiarize yourself with its melody and tonality.
- Identify the note that feels like "home" or the tonal center. This note often occurs at the beginning and end of phrases or sections.
Determine the major or minor quality:
- Listen for the overall mood of the song. If the song sounds happier and brighter, it's likely in a major key. If it sounds sadder or more somber, it's likely in a minor key.
Count the number of sharps or flats:
- Starting from the tonal center, count the number of sharps or flats in the song's melody or chords. Sharps raise a note by one half step, while flats lower a note by one half step.
Refer to the key signature chart:
- Once you've counted the sharps or flats, refer to a key signature chart to determine which key signature corresponds to the observed patterns.
Confirm your choice:
- Play the song again with the chosen key signature to see if it sounds correct. The song should sound harmonious and in tune. If it doesn't, you may need to reevaluate your choice of tonal center or key.