Most audio software will let you click on a position on a volume slider and the button indicating the volume level on that slider will move over towards that spot. Not so with parole media player. You must grab the actual slider button and drag it towards where you need it or position mouse over the slider and if you have a mousewheel you can adjust by rolling mousewheel. This stumped me for two seconds after first trying to use it.
Affects me also, one more vote.
Parole is currently not using the normal scale-widget anymore to display/adjust the volume. Please test again with git-master. Also: that behavior (not being able to change the value of a scale by simply clicking it) is normal in Gtk, Parole just circumvents it for the playbar.