LTSPICE - Simulating variable load?

I would like to work on a discrete regulator circuit, and an important criterion is how well it does when the load (e.g. a DAC or pre-amp circuit) alters its power use rapidly (typically at audio frequencies (*)).

Any suggestions as to how I represent such a load in LTSpice?

BugBear

(*) yeah, I know, some extreme class-A amplifier circuits don't do this.
 
A standard current source can be set up to generate a pulse waveform while running a transient analysis. And you can characterize the output impedance vs frequency of your reg using an AC analysis, driving the reg output with a current source.