Each letter is a key on the on-screen piano below. Lowercase letters are white keys, capital letters are black keys. Open the piano and press them in order — no sheet music needed.
C D E C · C D E C · E F G · E F G · G A G F E C · C G CFrere Jacques is the same four notes repeated, then the same three notes repeated, then a descending scale. Nothing in it is new after the first bar. That repetition makes it the single best song for working on even tone: you hear immediately if one note is louder or shorter than its neighbours.
t y u t, then the same four again, then u i o twice, then o p o i u t, and finish with t o t.
Because the melody repeats every two bars, so a second player can start the same line while the first is still going. Learning it in a round forces you to keep strict time.