Now that all the major components are finished, you can assemble them into a master composition:
Create a new composition named Heartbeat Master in your Comps folder using the NTSC DV, 720x480 comp preset, with Duration 10;00 seconds.
Add the Heart Monitor composition to the Heartbeat Master Timeline at time 0;00.
To fade in the Heart Monitor layer, add a 0% Opacity keyframe at time 0;00 and a 100% Opacity keyframe at time 0;15.
To fade out the Heart Monitor layer, add a 100% Opacity keyframe at time 8;15 and a 0% Opacity keyframe at time 9;29.
Add the Car Movie composition to the Heartbeat Master Timeline at time 0;00, above the Heart Monitor layer.
To fade the Car Movie layer in and out, copy the Heart Monitor layer's Opacity keyframes, paste them onto the Car Movie layer at time 0;00, and then move the third Opacity keyframe to time 5;00 and the fourth keyframe to time 6;00.
Adding Opacity keyframes to fade the layers in and out
Set the Car Movie layer's Blending Mode to Add in the Timeline's Modes column. This mode combines the color in the layer with those below it.
The grid and heartbeat appear within the Car Movie layer.