Singing is not an activity! Singing is one of the clearest examples of embodied thought that I know of. The movement part of singing is a long, steady exhalation. A full breath and a relaxed, open throat are determined by how well we are balanced through our skeleton, so that our internal systems can move unimpeded by outer muscle tension. The rest of singing (onset of sound, pitches/notes, resonance, words, rhythm, communication) is a combination of awareness and thought. You are aware of your balance, your breath, your audience, your accompaniment. You decide to start your sound as you begin your long, steady exhalation. You think of all the notes, words and meaning that make up a phrase as you continue your exhalation. Your long steady exhalation then reflexively encourages a full, complete inhalation for the next phrase. Try this: sitting balanced on a chair, breathe out slow and steady while you think of a phrase of a song. Repeat a couple of times, each time letting the breath reflexively return. Then actually sing the phrase - what is the experience like? Is it similar to how you normally sing? How is it different?