  An analysis of semileptonic decays of $B$ mesons with the emission of a
single soft pion is presented in the framework of the heavy-quark limit using
an effective Lagrangian which implements chiral and heavy-quark symmetries. The
analysis is performed at leading order of the chiral and inverse heavy mass
expansions. In addition to the ground state heavy mesons some of their
resonances are included. The estimates of the various effective coupling
constants and form factors needed in the analysis are obtained using a chiral
quark model. As the main result, a clear indication is found that the $0^{+}$
and $1^{+}$ resonances substantially affect the decay mode with a $D^{\ast}$ in
the final state, and a less dramatic effect is also noticed in the $D$ mode. An
analysis of the decay spectrum in the $D^{(\ast)}-\pi$ squared invariant mass
is carried out, showing the main effects of including the resonances. The
obtained rates show promising prospects for studies of soft pion emission in
semileptonic $B$-meson decays in a $B$-meson factory where, modulo experimental
cuts, about $10^5$ such decays in the $D$ meson mode and $10^4$ in the
$D^{\ast}$ mode could be observed per year.
