“不看乐谱”可以翻译为“play without looking at the music sheet” 或者更简洁自然地表达为“play by ear” 。
“play by ear”是一个常用的英语习语，字面意思是“凭耳朵演奏”，实际含义是“不看着乐谱演奏；即兴演奏；凭感觉做事，随机应变” 。例如：
He can play the piano by ear.（他能不看乐谱弹钢琴。 ）
When it comes to dealing with unexpected problems, she tends to play by ear.（遇到处理突发问题时，她倾向于随机应变。 ）