Different connected devices will sometimes output media volumes at very different levels. For example: an Echo smart speaker is connected to Spotify through Alexa, and a local PC through Bluetooth. Playing media through Spotify on Alexa will be very loud. Playing media through the PC will be very quiet, at 100% volume on the PC.
Providing the option to set different device volumes for each connected device or service, through the Alexa app. This could look like this:
Spotify -- 50%
DEVICE-PC -- 100%