  A coalescence model using the observed properties of pre-stellar
condensations (PSCs) shows how an initially steep IMF that might be
characteristic of primordial cloud fragmentation can change into a Salpeter IMF
or shallower IMF in a cluster of normal density after one dynamical time, even
if the PSCs are collapsing on their own dynamical time. The model suggests that
top-heavy IMFs in some starburst clusters originate with PSC coalescence.
