  Electron dynamics in quantum dots manifests itself in spin-flip spectra
through electric dipole spin resonance (EDSR). Near a neutrality point
separating two different singlet charged states of a double quantum dot, charge
dynamics inside a $2\times2$ singlet manifold can be described by a
1/2-pseudospin. In this region, charge dynamics is highly nonlinear and
strongly influenced by flopping its soft pseudospin mode. As a result, the
responses to external driving include first and second harmonics of the driving
frequency and their Raman satellites shifted by the pseudospin frequency. In
EDSR spectra of a spin-orbit couplet doublet dot, they manifest themselves as
charge satellites of spin-flip transitions. The theory describes gross features
of the anomalous half-frequency EDSR in spin blockade spectra [Laird et al.,
Semicond. Sci. Techol. {\bf 24}, 064004 (2009)].
