Related chants in the Gregorian and Old Roman repertories differ mostly in ornamentation and surface detail. Old Roman chants are much more stepwise and gently undulating than Gregorian chants. Skips, even of thirds, are much less common in Old Roman chants than Gregorian. Gregorian chants often have a pentatonic structure, reinforced by their skips, while Old Roman chants are simpler in structure but more ornate, with more individual notes. Old Roman chants have intricate melodic motion within a narrow ambitus, with small, repeating melodic motifs, which are common in the Italian chant traditions such as the Ambrosian and Beneventan. Old Roman chants are often highly melismatic, with melismas blending into one another and obscuring the underlying melodic structure.