In the Arrange window's top-left corner, the button with the little running man enables Logic's Catch function. This button is called the Catch button, and when it's activated, the Arrange area's visible section follows the SPL as the song plays.
The Catch mode is available to all windows that show a progression of song events, such as the Matrix Editor, Event List, and Score Editor.
Use the Arrange window's horizontal zoom control to zoom in until bars 1 to 5 fill the Arrange area.
The song you're working on isn't very long. To see the Catch mode in action, the Arrange area's Regions must stretch beyond the Arrange area's right edge, so you need to zoom in.
Make sure that the Arrange window's Catch button is blue, which means it's activated. If the Catch button is not blue, click it.
Press the spacebar to play the song.
The SPL plays to the right edge of the Arrange area. When the SPL hits the right edge, the Arrange area jumps forward and the SPL commences playing from the left to right edges once more.
Without stopping the playback, at the bottom of the Arrange window, grab the scroll bar and scroll so that bars 1 to 5 are once again centered in the Arrange area.
The song continues to play, but notice that the Catch function has been disabled, and the Catch button is now gray (off). This demonstrates an important point: If you manually change the displayed area of a song (by either moving the scroll bar along the Arrange window's bottom edge or using the Magnifying Glass tool), the Catch function is automatically disabled, so the newly selected display area does not disappear.
Your song should still be playing. With the Catch function remaining off, single-click the Bar Ruler's lower portion at bar 1. The SPL jumps back to bar 1 and the song starts playing from that point. But more important, the Catch function is turned back on. This is an example of Logic's automatic Catch function, which activates the Catch mode each time the Play or Pause buttons are clicked, or whenever a playback command is initiated. Typically, you will want to keep the automatic Catch on, but you can disable it by choosing Logic > Preferences > Global Preferences pane > Catch tab and deselecting the "Catch when sequencer starts" and "Catch when moving song position" check boxes.