All other sound is simply a combination of multiple sine waves. While a true statement, this doesn't answer the question.
The technique of directly changing the individual sine waves within a complex wave. Great job!
The technique of indirectly changing the individual sine waves within a complex wave. You can change sounds by filtering, but this usually isn't referred to as spectral editing.
The combination of many sine waves with different frequencies, amplitudes, and phases, all of which change over time. This is the definition of spectrum, which gives sound color.