original key (of a song)
Abbreviation of 原曲キー. Used in music contexts, especially karaoke, to refer to the key in which a song was originally recorded.
See also: 原曲キー
The original key of this song is too high for me to sing.
I set it to the original key at karaoke.
Abbreviation of 原曲キー (original song key), combining 原 (original) and キー (key).