ivolume

Install command: 
brew install --cask ivolume

Name: iVolume

App to ensures that all songs are played at the same volume level

https://www.mani.de/en/ivolume/

Cask JSON API: /api/cask/ivolume.json

Cask code: ivolume.rb on GitHub

Current version: 3.9.0

Requirements: macOS >= 10.15

Analytics:

Installs (30 days)
ivolume 1
Installs (90 days)
ivolume 6
Installs (365 days)
ivolume 12