user33090: I am trying to render a 3 hour music loop with audio spectrum, and it takes me 16 hours to render. 
How do I fasten it up?

user24627: 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 "expensive" 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 "CUDA" 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...

user1950: Use aerender and start as many instances as your machine can support without running out of RAM or GPU RAM.
By default you'll see that After Effects doesn't always utilise all the power of your CPU. It is not multithreaded so most of your processors are sitting idle while you're waiting for it to render. However aerender (the command-line renderer that comes with AE) can be run multiple times, each instance working on an independant frame in parallel.
To use this method you need to be rendering to an image sequence (that's the best way to render anyway), and using the multi-machine render settings.
I document how I got a 4000% speed increase in a long render here

33090: <p>I am trying to render a 3 hour music loop with audio spectrum, and it takes me 16 hours to render. <br/>
How do I fasten it up?</p>
 24627: <p>Many things play a part in the time required for a render. The most significant are:</p>
<ul>
<li>Your Hardware (Ram, CPU and GPU are the most important parts)</li>
<li>The resolution of your composition</li>
<li>The Framerate of your composition</li>
<li>The Effects used and how &quot;expensive&quot; they are on the hardware</li>
<li>The Codec and Container you're using (like prores422 in .mov or h264 in .mp4)</li>
</ul>
<p>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...</p>
 1950: <p>Use aerender and start as many instances as your machine can support without running out of RAM or GPU RAM.</p>
<p>By default you'll see that After Effects doesn't always utilise all the power of your CPU. It is not multithreaded so most of your processors are sitting idle while you're waiting for it to render. However aerender (the command-line renderer that comes with AE) can be run multiple times, each instance working on an independant frame in parallel.</p>
<p>To use this method you need to be rendering to an image sequence (that's the best way to render anyway), and using the multi-machine render settings.</p>
<p>I document how I got a 4000% speed increase in a long render <a href="https://blob.pureandapplied.com.au/finally-managed-to-peg-my-cpu/" rel="nofollow noreferrer">here</a></p>
