What is ear training, and do singers need it?
Ear training is practice at recognising what you hear: how far apart two notes are, whether a note is higher or lower than the last, rhythms and chords. Singers need it more than most instrumentalists, because there are no keys or frets to press: you have to hear the next note in your head before you can sing it. A few minutes of naming intervals makes it easier to learn melodies, to sing harmonies and to notice when you have drifted off the note.