Tone Deafness, Tone Deaf, Off Key
noun, な adjective, の adjective
If you're stupid when it comes to sounds, then you're tone deaf.
おんち
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
音痴なので、カラオケは苦手です。
I’m tone-deaf so I’m bad at karaoke.