A method comprising: in a vehicle equipped with a vehicle sound system and a continuously variable transmission, CVT, determining a virtual fixed gear ratio; determining if sound correction is necessary, and, if sound correction is necessary, then calculating an instantaneous value of a current gear ratio of the CVT, setting the virtual fixed gear ratio to the instantaneous value of the current gear ratio of the CVT and maintaining the virtual gear ratio constant at the calculated instantaneous value of the current gear ratio until a gear ratio deviation of the virtual fixed gear ratio relative to the current gear ratio exceeds a gear ratio deviation value; determining a virtual RPM based on the virtual fixed gear ratio; wherein the virtual fixed gear ratio is determined based on a current gear ratio of the continuously variable transmission which varies continuously in time as a function of an actual, measured RPM and vehicle speed, and wherein the virtual RPM changes with the vehicle speed when the actual RPM remains constant; generating a set of harmonic signals based on the virtual RPM, the harmonic signals being sine-wave signals proportional to harmonics of the virtual RPM; processing the harmonic signals to produce a set of processed harmonic signals; and in the vehicle sound system, transducing the processed harmonic signals to acoustic energy thereby to produce an engine sound within a passenger cabin of the vehicle; wherein determining if sound correction is necessary comprises: determining that a change in actual RPM, Δ RPM, does not exceed a maximum value Rmax, and determining that a change in actual vehicle speed, ΔVSP, exceeds a minimum value, Vmax. in a vehicle equipped with a vehicle sound system and a continuously variable transmission, CVT, determining a virtual fixed gear ratio; determining if sound correction is necessary, and, if sound correction is necessary, then calculating an instantaneous value of a current gear ratio of the CVT, setting the virtual fixed gear ratio to the instantaneous value of the current gear ratio of the CVT and maintaining the virtual gear ratio constant at the calculated instantaneous value of the current gear ratio until a gear ratio deviation of the virtual fixed gear ratio relative to the current gear ratio exceeds a gear ratio deviation value; calculating an instantaneous value of a current gear ratio of the CVT, setting the virtual fixed gear ratio to the instantaneous value of the current gear ratio of the CVT and maintaining the virtual gear ratio constant at the calculated instantaneous value of the current gear ratio until a gear ratio deviation of the virtual fixed gear ratio relative to the current gear ratio exceeds a gear ratio deviation value; determining a virtual RPM based on the virtual fixed gear ratio; wherein the virtual fixed gear ratio is determined based on a current gear ratio of the continuously variable transmission which varies continuously in time as a function of an actual, measured RPM and vehicle speed, and wherein the virtual RPM changes with the vehicle speed when the actual RPM remains constant; wherein the virtual fixed gear ratio is determined based on a current gear ratio of the continuously variable transmission which varies continuously in time as a function of an actual, measured RPM and vehicle speed, and wherein the virtual RPM changes with the vehicle speed when the actual RPM remains constant; generating a set of harmonic signals based on the virtual RPM, the harmonic signals being sine-wave signals proportional to harmonics of the virtual RPM; processing the harmonic signals to produce a set of processed harmonic signals; and in the vehicle sound system, transducing the processed harmonic signals to acoustic energy thereby to produce an engine sound within a passenger cabin of the vehicle; wherein determining if sound correction is necessary comprises: determining that a change in actual RPM, Δ RPM, does not exceed a maximum value Rmax, and determining that a change in actual vehicle speed, ΔVSP, exceeds a minimum value, Vmax. determining that a change in actual RPM, Δ RPM, does not exceed a maximum value Rmax, and determining that a change in actual vehicle speed, ΔVSP, exceeds a minimum value, Vmax.