I have a lot of Sonos speakers throughout my house, and it would be nice to be able to use a single volume control for all speakers at once. This is not currently practical, because each speaker has its own relative volume profile that depends both on the speaker type and on other factors, such as room size and placement.

It would be great to be able to spend some time creating snapshots of various volume settings, so that all the speakers have the same relative volume throughout the house, and then for the Sonos app to create volume curves from those snapshots. I think this could be done pretty easily with just three snapshots, one for low volume, another for medium volume, another for high volume. Then, the app would calculate volume curves for each speaker, at which point you should be able to control the volume for all speakers at once with a single slider/knob/etc, with the relative volume of each speaker remaining consistent at all times.

I really can't imagine a scenario where people would want different speakers to play at different relative volumes, or at least it would seem to be an edge case. Making snapshots for calculating volume curves would be a manual process that takes a little time, and I'm sure plenty of people would never bother doing it, but it would be so worth it for those who do.