Temperature-modulated differential scanning calorimetry (TMDSC) generated with a centrosymmetric saw-tooth oscillation can be considered to be a sinusoidal modulation with multiple frequencies. Different harmonics of the Fourier series of the heat-flow rate and heating rate of a single sawtooth-modulation can be deconvoluted to extract data pertaining to different frequencies. In order to give the higher harmonics similar amplitudes, a complex, but simple-to-program, sawtooth-modulation is generated for the harmonics 1,3,5,7 and 9. In this fashion a single experiment can produce a frequency-dependent analysis under identical thermal history. Application of this method to TMDSC includes the calibration for heat capacity determination of high precision, even if steady state and a negligible temperature gradient are not achieved. The measurement of the frequency (ω) dependence of the heat-flow rate (A_HF) and sample temperature (A_Ts) allows to evaluate the expression: CP = AHF /( ATs νω) [1 + (τνω)2 ]0.5 where the relaxation time τ is to be determined empirically from the multiple data generated by the single run. Typical values for the relaxation time for commercial calorimeters are between 3 and 9 s rad^-1. Frequency-dependent, apparent reversing heat capacities in the glass transition region and within first-order transition regions may also be analyzed to study local equilibria in globally metastable polymeric solids.