also: みみコピー
noun
playing by ear; transcribing by ear
Colloquial term used among musicians for learning or transcribing music by listening, without sheet music.
彼は耳コピで難しいギターソロを完璧に弾いた。
He played the difficult guitar solo perfectly by ear.
耳コピで採譜するのは時間がかかるけど、耳が鍛えられる。
Transcribing by ear takes time, but it trains your ear.
採譜 is a more formal term for transcription, not necessarily by ear.
耳で覚える means 'learn by ear' in a general sense, not limited to music.
Compound of 耳 (ear) and コピー (copy), literally 'ear copy'. A colloquial coinage from music circles.