There's been some really second-rate attempts to make a stereo sound from mono recordings [duophonic etc.]in the past, but at last there's a method being applied that has an almost magical effect - digitally extracted stereo [audio spectral editing and sound source separation.]
"The fundamental difference between mono and stereo is one of spatial perspective: because it employs only a single signal channel for recording and reproduction, mono can convey an audible image reliably in only one dimension - that of front-to-back depth. Since by definition stereo employs two (or more) signal channels, it can add the dimensions of width and even height. These are the basic technical considerations. How they are implemented, however, is what turns the technology into art." ~Ron Screicher
monotoSTEREO.info is dedicated to providing a collection of resources for individuals upmixing older mono music recordings to stereo. Various attempts have been made through the years to "simulate" stereo from mono sources. This website will focus on audio spectral editing, sound source separation, and other related tools and processes used specifically for the purpose of upmixing mono source material to stereo, with the goal of creating stereo mixes that are virtually indistinguishable from stereo mixes created using multitrack session tapes, had they existed.
~ Christopher Kissel, Independent Audio Engineer.