  Characteristics of multi-particle production in proton-proton collisions at
sqrt(s) = 7 TeV are studied as a function of the charged-particle multiplicity,
N[ch]. The produced particles are separated into two classes: those belonging
to jets and those belonging to the underlying event. Charged particles are
measured with pseudorapidity abs(eta) < 2.4 and transverse momentum pt > 0.25
GeV. Jets are reconstructed from charged-particles only and required to have pt
> 5 GeV. The distributions of jet pt, average pt of charged particles belonging
to the underlying event or to jets, jet rates, and jet shapes are presented as
functions of N[ch] and compared to the predictions of the PYTHIA and HERWIG
event generators. Predictions without multi-parton interactions fail completely
to describe the N[ch]-dependence observed in the data. For increasing N[ch],
PYTHIA systematically predicts higher jet rates and harder pt spectra than seen
in the data, whereas HERWIG shows the opposite trends. At the highest
multiplicity, the data-model agreement is worse for most observables,
indicating the need for further tuning and/or new model ingredients.
