Visualizer MusicTech Edition is a specially compiled free edition of Nugen Audio's Visualizer available on the MusicTech Magazine cover-mount DVD or via this link. There is also a two-page tutorial on taking spectral imprints within the MusicTech magazine itself (Issue 55).
"To fully appreciate how your mix is working on every level, a spectrum analyser is an essential tool. To this end, NuGen Audio has compiled a special edition of its Visualizer analysis plug-in, exclusively for MTM readers. Follow the workshop on pages 8 and 9 to find out how it can dramatically improve your mixes."