Although a title sequence may be modified during a series to update cast changes or incorporate new "highlight" shots from later episodes, it will tend to remain largely the same for an entire season. Some shows have had several quite different title sequences and theme music throughout their runs, while in contrast some ever-popular shows have retained their original title sequences for decades with only minor alterations. Conversely, retaining a series' original title sequence can allow a producer to change many key elements within a programme itself, without losing the show's on-screen identity. Other variations include changing only the theme music whilst keeping the visuals or vice versa.