The modulation of a ramped potential applied to a voltammetric electrode evokes two responses: a quasiperiodic 'ac' current of the same periodicity as the modulation, and a perturbation, of the underlying dc current. The latter is the subject of this article. Reasoning by analogy with an analytical result for reversible square-wave-modulated linear-potential-scan voltammetry, a sequence of credible arguments has allowed prediction of the de current for modulations of any waveform and of any amplitude. Applications to staircase voltammetry and to modulated cyclic voltammetry are included.