You've already tried the track's Volume slider, but there are other volume controls you should know about. In Mixere, the volume of a track is affected by at least four controls, and possibly five:
Pressing Mute silences the track. Pressing Solo silences all other tracks, except for tracks that are already soloed. Note that solo overrides or "trumps" mute, in other words, solo works even if the track is currently muted.
Each document has its own Volume slider, which affects the volume of all the tracks in the document. To show or hide the current document's Volume slider, select Volume from the View menu, or press V.
The Crossfader fades between two documents. To show or hide the Crossfader, select Crossfader from the View menu, or press X. The Crossfader contains two list boxes, Source A and Source B, which are used to select the documents you want to crossfade between. There's also a button for selecting the crossfade type: linear, or "dipless" (DJ style).
Master Volume affects the volume of the entire Mixere application. To show or hide the Master Volume slider, select Master Volume from the View menu, or press Shift+V.
Volume, Master Volume, and Crossfader all contain automation sliders. In other words, you can program them, using the same methods discussed above.