How do I render faster in AE?
Many things play a part in the time required for a render. The most significant are:

Your Hardware (Ram, CPU and GPU are the most important parts)
The resolution of your composition
The Framerate of your composition
The Effects used and how &quot;expensive&quot; they are on the hardware
The Codec and Container you're using (like prores422 in .mov or h264 in .mp4)

First off, check how much RAM is dedicated to After-Effects in its preferences. You should at least dedicate half your RAM to AE. If it's less than 8GB, you might want to consider getting more RAM. Also, check if you have hardware acceleration enabled. It's usually called &quot;CUDA&quot; for Nvidia graphics cards and could increase the speed of your rendering.
Next, check your resolution. Audio-Spectrum videos should be alright in 1080p, so don't render in 4k or 6k.
A 3 Hour video does require a rendertime of about 16 hours though, when you use an expensive effect such as an audio spectrum. If you really wanna cut down the time, you'd need a render-farm, I assume...