Sequence of synthetic spectra at five different evolutionary stages (marked by the identifiers also used in Fig. 1 and Table 1) of a massive star with initial mass 60 M_⊙ evolving quasi-homogeneously at Z = 0.1 Z_⊙ (Marchant track I). The continuum levels and the zero lines are indicated by horizontal thin gray lines. The time series starts at the bottom with the spectrum of the model at the ZAMS. To facilitate a comparison with observed spectra, the model spectra are convolved with a Gaussian profile with a FWHM of 1.0 Å.