To start making a Music Visualizer is incredibly easy in Quartz Composer.
All you have to do is open up Quartz Composer, click on the File menu and select New from Template.
This will open up the Template dialog box from which you can select the Music visualizer template.
This will create a new music visualizer based upon that template. The default composition opens a Viewer and Editor window showing the Root Macro Patch and the visualization in a Custom ratio view. One of the great features of Quartz Composer is just how elastic its rendering space can be.In Custom Ratio mode you are able to set the composition to alomost any rectangualr relationship. When set to a fixed ratio, like 4:3 or 16:9 or 16:10, the viewer window will keep to a strict size ratio and won't endlessly expand or shrink.
Please note, unless you are running iTunes with the visualizer on, you won't be able to see anything happening in your new composition.
This is because without audio data, the Audio Spectrum Macro Patch has nothing to work with.
The resulting music visualizer is pretty simple at first glance, but merits further study. The Root Macro Patch shown in the editor window comprises all the protocol inputs, like audio peak, spectrum, track info, signal and position that are required to make a music visualizer.
The outputs from these protocol inputs are then changed into data input for creating or affecting graphic resources and objects and text strings for track information and running time within other macro patches nested within the Audio Spectrum macro patch. There is another macro patch for HUD - Heads Up Display. Finally, there is a Clear patch which basically gives us the black background.
Please note, you can apply a protocol set to a compostion at any time to begin turning it into a music visualizer. Going down the template route is by no means the only way to make an iTunes visualizer. It is a convenient and 100% effective method. Although the resulting composition is fairly simple, being a bar graph of the spectrum throughput, it can easily be altered.
Lets take a closer look at the visualizer composition.