  We propose a microscopic model for a nanoelectromechanical system made by a
radio-frequency driven suspended carbon nanotube (CNT) in the presence of an
external magnetic field perpendicular to the current. As a main result, we show
that, when the device is driven far from equilibrium, one can tune the CNT
mechanical properties by varying the external magnetic field. Indeed, the
magnetic field affects the CNT bending mode dynamics inducing an enhanced
damping as well as a noise term due to the electronic phase fluctuations. The
quality factor, as observed experimentally, exhibits a quadratic dependence on
external magnetic field strength. Finally, CNT resonance frequencies as a
function of gate voltage acquire, increasing the magnetic field strength, a
peculiar dip-peak structure that should be experimentally observed.
