The manual page says:
The module supervp.sourcefilter~ performs source-filter cross-synthesis to two incoming sound streams, imprinting the spectral envelope of the ‘filter’ stream (right inlets) to the ‘source’ stream (left inlets).
I am trying to wrap my head around the notion of a spectral envelope. Having played with the supervp.sourcefilter~ overview patch, it is clear to me that source stream definitely obtains “an” envelope from the filter stream. However, it does not sound like a conventional gain envelope and it sounds different than what a gain envelope would do. What is a spectral envelope in layman’s terms, if possible?