[17.10] Installing legacy pulseaudio-equalizer

[there.is.only.xul]

But why?
Let's understand first why anyone want an audio equalizer in your system:

• It doesn't require additional hardware
• Often presets come included with software equalizers
• Audio can be improved for all software rather than only for your media player through its built-in equalizer
• Depending on environment the listening experience could be improved by adjusting the sound curve
• Settings can be configured per-genre with whatever preferences used as a base

Any user could install pulseaudio-equalizer today, and be done with it. Except not, because here are the problems with the current package from Ubuntu's repositories;

• It doesn't work out of the box
• Even after configuration it needs to be invoked
• After removing it out of frustration it is more-than-likely pulseaudio becomes broken
• It comes with no presets unlike the legacy version which came before it

Before proceeding...
Because of these above reasons, there's no reason I can recommend installing the current pulseaudio-equalizer to anyone. Fortunately, the older, legacy version of it exists, and it can be held back to keep apt from ruining system audio. As always, there is a risk of system instability and failure to upgrade when a new distribution is released, so before upgrading the installed distribution, there will be additional steps presented below to ensure a smooth upgrade process, or at least prevent the end-user from being at fault for catastrophic system failure.

Additionally, it will be assumed the current distribution version to be affected is Artful Aardvark (17.10). If not, there is no need to edit the .list file obtained by following the steps below so that can be skipped.

Installation
Open a terminal and input the following;

sudo apt-add-repository ppa:nilarimogard/webupd8
sudo gedit /etc/apt/sources.list.d/nilarimogard-ubuntu-webupd8-*.list

Replace gedit with whatever the system's graphical text editor is.

Duplicate the lines shown for artful (or greater) and paste, replacing the current distribution name for the additional two lines with zesty, so that packages for both the current distribution and Zesty Zapus are retrieved. After, return to terminal and continue with the following;

sudo apt update
sudo apt-get install pulseaudio-equalizer=2.7.0.2-5~webupd8~xenial0
sudo apt-mark hold pulseaudio-equalizer
pulseaudio-equalizer-gtk

Enable the equalizer and make whatever changes desired (preferably while listening to something). Whatever other changes performed with this is at the end-user's discretion.

Conclusion
There really isn't much to say. More options are better, and a software equalizer similar to those used in Microsoft Windows makes for a nice addition to improve the Ubuntu experience. But since this guide detailed how to install an older version and keep apt from complaining about it, Here's what needs to be done between distribution upgrades to make sure the upgrade process runs smoothly;

sudo apt-mark unhold pulseaudio-equalizer
sudo aot-get remove pulseaudio-equalizer
sudo apt-get autoremove