Combining Logic 's Catch and Link modes can greatly increase the usefulness of multi-window Screensets, but it is not always clear, especially to new users, how the various options work.
The options during playback for each open window are controlled by two buttons at the top left-hand corner of the window: the Catch button ('running man' icon) and the Link button ('linked chain' icon). I'll start with a brief description of those buttons' various states, then move on to demonstrate some multi-window examples that make use of different modes.
The Catch button has two modes: it is on when the button is blue and off when it is gray. When Catch is on, the window automatically scrolls to keep the Song Position Line (SPL) in view. Two methods of scrolling are supported; one keeps the SPL centred while the data scrolls behind it, and the other jumps to reposition the SPL at the left-hand edge of the window each time it reaches the right-hand edge.
The first of these methods is called Scroll In Play, and it can be switched on via each window's View menu. Although it can seem more intuitive to have Scroll In Play switched on all the time, it does require more graphic processing, so may cause problems in complex Songs where your computer's processor is already under pressure. Note that scrolling in the Event List is vertical, and scrolling in the Score window is page-wise when in Page Edit view.
The Catch mode is available in all windows that have a time dimension; that includes the Arrange window and each of the editors. The Audio, Project Manager, Track Mixer, Transform, Transport, and Environment windows have no time dimension, and therefore no Catch button.
The Link button has three modes: Link when the button is red, Contents Link when the button is orange, and neither when the button is gray. Contents Link mode is activated by double-clicking the button. The key to understanding the difference between the Link and Contents Link modes is knowing which windows display objects, which display the contents of those objects, and which display both. Three kinds of objects are relevant for our purposes: MIDI sequences, which hold MIDI data; audio regions, which hold audio data; and folders, which can hold MIDI and audio regions as well as other folders.
The Arrange window, Event List, and Hyper Edit window can display audio regions and MIDI sequences as well as Folders. The Event, Hyper Edit, Matrix Edit, and Score windows can display the contents of MIDI sequences. (The Event list and Hyper Edit window are the only windows capable of displaying both MIDI sequences and their contents.) The Arrange and Audio windows and the Event List can show audio regions. The Sample Editor window displays the contents of audio regions.
A window in Link mode will always display whatever data is selected in another window, if it is capable of displaying that kind of data. For example, a Linked Event List window will display any sequence, region, or folder selected in an Arrange window or another Event List. Alternatively, it will display any MIDI data selected in any MIDI editor, such as a Matrix Edit or Score window.
A window in Contents Link mode will always display the contents of an object selected in another window, if it is capable of displaying that kind of data. For example, a Contents Linked Arrange window will display the contents of any Folder selected in another Arrange window or Event list. A Contents Linked Track Mixer window will display the channel strips of tracks inside any Folder selected in an Arrange window — a great way to set up submixes. A Contents Linked Matrix Edit window will display the MIDI data in a MIDI sequence selected in an Arrange window or Event List.
It is a common misconception that the window in which a selection is made must be active (topped) for the Link modes to apply. Actually, the selection can be made in active, background, or floating windows — it doesn't make any difference. Also keep in mind that if you click and hold for a moment (called 'long-clicking') in a window that is not topped, it does not become topped. You can, therefore, make use of Linking and Contents Linking without ever changing the topped window.
A common and very useful three-window Screenset consists of an Arrange window and an Event list in Link mode, with another MIDI editor (Matrix, Score, or Hyper Edit) in Contents Link mode. Selecting objects in the Arrange window reveals them in the Event list, where their position and length can be numerically edited. Selecting MIDI regions in the Arrange window or Event list makes their data available for editing in the chosen MIDI editor. Finally, selecting MIDI events in the chosen MIDI editor reveals them for numerical editing in the Event List.
For audio editing, replace the second MIDI editor in the above Screenset with a Sample Edit in Link mode. Selecting audio regions in either the Arrange window or Event list will reveal their contents in the Sample editor. You might also replace the Event list with an Audio window in Link mode. You lose numerical editing of the audio region positions, but you gain access to all audio files and their regions, not just the ones being used.
Notice that the Audio window and Sample Editor don't have a Contents Link mode. The Audio window only displays audio objects and the Sample editor only displays the contents of audio regions, so the Link button Links the Audio window with other object-displaying windows (such as the Arrange window and Event list) and it Contents Links the Sample Edit with object-displaying windows (such as the Audio window).
Catch and Contents Link modes used together have a special function for the MIDI editors (though not for the Sample Edit). Once a MIDI region is selected on an Arrange track, the contents of other MIDI regions on that track will automatically be displayed as the SPL passes over them — in other words, as they play.
The basic rules of thumb when opening multiple windows in a Screenset are to use Link mode to synchronise MIDI editors to each other so that each displays the same data for editing. Use Contents Link mode to synchronise a window that displays data (such as a MIDI editor or the Sample Editor) with a window that displays objects (such as the Arrange window). Also, use Contents Link mode to display the contents of Folders selected in an Arrange window or Event list in another Arrange window or Event list. Finally, turn Catch on to keep the data under the SPL always in view.