Turn down app volume in Lollipop while not in app? In Lollipop the volume buttons seem to be context sensitive.  In some apps the volume buttons adjust ringer volume, while in others it adjusts app volume.  This usually works well, but I often want to turn app volume down before I open an app with sound to avoid disturbing those around me.  

Is there a way to force the application volume down without being in a "app volume context" for lack of a better word?
The only way I'm aware of to set media volume outside of an app is to go into the Settings. Specifically, Settings → Sound &amp; notification should give you separate sliders for each of the available volume channels. You'll want to turn down the top one ("Media volume").

On some custom ROMs it may be possible to do this slightly differently. Older versions of CyanogenMod had an option to expand the volume slider overlay, so you could hit the volume button and then manually adjust the appropriate slider from the overlay without having to go into your settings. Other ROMs may include something similar, but I cannot state definitively any that do.

As an aside: I'm not sure that this is unique to Lollipop. I believe it's been like this for a while (as long as I can remember, anyway).