There’s no such thing as a bad note, but you may find that some notes give you trouble. For example, they might be hard to sing, and I’m quite sure I’m going to draw some fire for this, but here are two notes that come up in your melodies that you might want to be aware of. A reasonable person might assume that because your song is in C, you can sing a C wherever you want to, and you totally can, but if you sing a C when you’re playing a G chord, you might sense that something doesn’t fit.
The most stable landing spot on any chord is a chord tone. There is no C in a G chord. The B is the third of the chord, and the C is a suspended fourth, and if both of those two are present, they’re going to body check each other, and your vocal performance may find itself in the middle.
You’ll also experience this singing a C over an E minor. The C is a half step above the B, and with any minor chord, playing a note a half step above the fifth puts your ear in competition for another chord, in this case, a C major. So two notes to look out for, a half step above the third of a major chord, the half step above the fifth of a minor chord.
They can be utterly beautiful, but if you find yourself with a problem you can’t quite put your finger on, it might just be with a closer look, and you can share that with someone who belongs in a Beat Kitchen class.