  Minimally empirical G4-like composite wavefunction theories [E. Semidalas and
J. M. L. Martin, \textit{J. Chem. Theory Comput.} {\bf 16}, 4238-4255 and
7507-7524 (2020)] trained against the large and chemically diverse GMTKN55
benchmark suite have demonstrated both accuracy and cost-effectiveness in
predicting thermochemistry, barrier heights, and noncovalent interaction
energies. Here, we assess the spectroscopic accuracy of top-performing methods:
G4-\textit{n}, cc-G4-\textit{n}, and G4-\textit{n}-F12, and validate them
against explicitly correlated coupled cluster CCSD(T*)(F12*) harmonic
vibrational frequencies and experimental data from the HFREQ2014 dataset, of
small first- and second-row polyatomics. G4-T is three times more accurate than
plain CCSD(T)/def2-TZVP, while G4-T$_{\rm ano}$ is two times superior to
CCSD(T)/ano-pVTZ. Combining CCSD(T)/ano-pVTZ with MP2-F12 in a parameter-free
composite scheme results to a root-mean-square deviation of ~5 cm$^{-1}$
relative to experiment, comparable to CCSD(T) at the complete basis set limit.
Application to the harmonic frequencies of benzene reveals a significant
advantage of composites with ANO basis sets -- MP2/ano-pV\textit{m}Z and
[CCSD(T)-MP2]/ano-pVTZ (\textit{m} = Q or 5) -- over similar protocols based on
CCSD(T)/def2-TZVP. Overall, G4-type composite energy schemes, particularly when
combined with ANO basis sets in CCSD(T), are accurate and comparatively
inexpensive tools for computational vibrational spectroscopy.
