Pay attention to how composers use these functional harmonies with respect to the scalar lines within each passage. Tonal phrases tend to move from tonic (roman numeral I, built on scale degree 1) to dominant (roman numeral V, built on scale degree 5), and back, with other harmonies, especially ii and IV, used to prepare the dominant. Labels harmonies according to the root, with chords built on a given scale degree assigned a roman numeral corresponding to that number.
