This article explores the new unit generatorss that integrate the Csound 5 music programming language for frequency-domain signal (fsig) processing. This framework for spectral signals was introduced to Csound 4.13, by Richard Dobson and further extended by Victor Lazzarini in version 5. The latest release of Csound incorporates a variety of new opcodes for different types of spectral manipulations. This article introduces the fsig framework and the analysis and resynthesis unit generators. It describes in detail the different types of spectral processing made possible by these new opcodes.