On many occasions we use more than one monitor for our Mac, but they are not always the recommended by Apple, more than anything for the price they have. So when we want to control some settings of that additional monitor, we find ourselves in the position of not being able to do it in the same way we do it on our Mac. For example, adjust the brightness. ControlMonitor, is an application that will help you with this task.
ControlMonitor lets you adjust the brightness of that additional monitor just like you do on the Mac
Any of the Macs have some dedicated keys for adjusting the screen brightness. The problem arises when we add an additional monitor. We cannot adjust certain details of it from the keyboard and although some screens have a button dedicated to it, it is much easier from the keyboard. ControlMonitor is a free application that allows you to perform these tasks In a simple way.
When we start to download the application, will request a special permit to access those additional screens. Once we give that permission and the app is installed we can click on the icon in the menu bar and use the slider to change the brightness of the external monitor. To use the brightness keys, make sure that the external screen is active.
If we have more than one screen, by default, ControlMonitor does not let us select all the screens at the same time. We must select them manually, each of them, to be able to adjust the brightness of it. Making sure that you always have the one you want to modify active. But we can modify this parameter. We open the application preferences and go to the "Screen" tab. In this way, The next time you touch the keyboard brightness keys, the brightness will change for all screens at the same time.
MonitorControl It also works for the audio output integrated and the port to which it is connected allows macOS to send audio to it, you can use the volume keys on the keyboard to control the volume of both the internal speakers and the monitor speakers themselves.