VOLT (Visual OpenType Layout Tool) is a utility distributed freely by Microsoft whose only purpose is to add OpenType tables to TrueType fonts. VOLT runs only under Windows. A web page  at Microsoft's site is devoted to it, but the software itself cannot be downloaded from that page. To obtain it, one must first register for the discussion forum:
The links for downloading the software appear on this forum's web site.
The "project" window in VOLT (see Figure 14-6) includes, from top to bottom, some menus, a row of buttons, three graphical areas, and another row of buttons. The three graphical areas will contain:
The hierarchy of scripts, languages, features, and lookups in the font
The complete list of lookups
The list of glyph classes
Aside from the project window, there are also windows for glyphs, substitutions, positionings, glyph classes, and testing.
General mode of operation
We open a font by using the Open button. This operation will delete all the existing OpenType tables in the font. Only the tables specific to VOLT will be preserved and interpreted, which means that if we have begun to produce OpenType tables with other software, our work will be lost[14-6] and we shall have to start again from scratch.
[14-6] In theory there are ...