  We present Ekster, a new method for simulating star clusters from birth in a
live galaxy simulation that combines the smoothed-particle hydrodynamics (SPH)
method Phantom with the $N$-body method PeTar. With Ekster, it becomes possible
to simulate individual stars in a simulation with only moderately high
resolution for the gas, allowing us to study whole sections of a galaxy rather
than be restricted to individual clouds. We use this method to simulate star
and star cluster formation in spiral arms, investigating massive GMCs and
spiral arm regions with lower mass clouds, from two galaxy models with
different spiral potentials. After selecting these regions from pre-run galaxy
simulations, we re-sample the particles to obtain a higher resolution. We then
re-simulate these regions for 3 Myr to study where and how star clusters form.
We analyse the early evolution of the embedded star clusters in these regions.
We find that the massive GMC regions, which are more common with stronger
spiral arms, form more massive clusters than the sections of spiral arms
containing lower mass clouds. Clusters form both by accreting gas and by
merging with other proto-clusters, the latter happening more frequently in the
denser GMC regions.
