  We review several aspects of the phenomenology of P-wave $\bar q Q$ mesons:
mass splittings, effective strong couplings and leptonic constants. We also
describe a QCD sum rule determination to order $\alpha_s$ of the form factor
$\tau_{1/2}(y)$ governing the semileptonic $B$ decays to the charm doublet with
$J^P=(0^+_{1/2},1^+_{1/2})$.
