Tuneless
/ˈtuːnləs/
Definition 1 of 1
Pro Tip 1/3Lack of Harmony
Tuneless implies music lacks harmony and is hard to listen to, not just simply unskilled. 
Despite her efforts, her tuneless rendition of the anthem made the crowd wince.
Pro Tip 2/3Subjective Perception
What sounds tuneless to one person might not to another; it's often a personal opinion. 
My dad finds jazz tuneless, but I love its improvisational sound.
Pro Tip 3/3Music Context
Tuneless usually describes musical elements, but it may refer to other sounds meant to be musical. 
The tuneless beeping of the old computer was a far cry from the harmonious music it was designed to play.