I understand that Indicators are still working but not supported out of box on 15.04? What’s the current method? Any Mate Tweak options?
And with the Indicator volume applet is it possible to use the multimedia keys to raise the volume beyond 100%, like in Ubuntu+Unity?
Thanks!
Concerning the indicators, they have already answered this question. Here is the link brother : Enabling Indicators in Ubuntu MATE 14.10 and 15.04
These tips support 14.10 and 15.04 versions.
Have a nice day 
No on my computer at least. I need to open the sound settings dialog and move the slider to use a setting over 100%. So in this regard, there is no advantage to using the sound indicator as the existing volume control and sound settings can do the same thing. One other thing: the sound indicator applet does not show any indication the level is over 100, but the existing volume control shows the correct level in the tooltip (130%, for example). In addition, the existing mate volume control is adjustable with the mouse scrollwheel by just hovering over the panel icon, but when using the indicator applet this does not work in MATE (bug report #1421436).