Adjust macOS system volume with precision. Download
vol <number between 0–100>to set system volume to the given level.
vol +<number between 0–99>to adjust system volume by the given increment.
vol ?to check the current volume level.
If no notification banners are pushed after commands (esp.
vol ?) as they should do, then check the notification centre to see whether Do Not Disturb mode is triggered, and make sure that the notification style for Alfred is either Banners or Alerts in System Preferences.
This workflow is also published on Packal.