...
Right-clicking on a Seismic Line or a Seismic Brick Cube and selecting "Seismic Attribute Calculator..." pops up the following dialog:
The Seismic Attribute Calculator makes it possible to combine Seismic + up to 3 Seismic Attributes into a weighted combined Attribute.
From the Variables drop-down list you can choose from different variables such as I, inline trace position. Hoovering over a variable name brings up a description.
From the Functions drop-down list you can choose from many different mathematical functions such as abs(). Hoovering over a function name brings up a description.