  We derive the connected tree-level part of 4-point holographic correlators in
AdS$_3\times S^3\times \mathcal{M}$ (where ${\cal M}$ is $T^4$ or $K3$)
involving two multi-trace and two single-trace operators. These connected
correlators are obtained by studying a heavy-heavy-light-light correlation
function in the formal limit where the heavy operators become light. These
results provide a window into higher-point holographic correlators of
single-particle operators. We find that the correlators involving multi-trace
operators are compactly written in terms of Bloch-Wigner-Ramakrishnan functions
-- particular linear combinations of higher-order polylogarithm functions.
Several consistency checks of the derived expressions are performed in various
OPE channels. We also extract the anomalous dimensions and 3-point couplings of
the non-BPS double-trace operators of lowest twist at order $1/c$ and find some
positive anomalous dimensions at spin zero and two in the K3 case.
