Control method of at least three electromagnetic stirrer devices (1', 1", 1''', 1'''') of the linear type acting on metallic material in the molten state contained inside at least one solidification mould (14, 14', 14") or contained inside a solidified metallic shell of at least one metal rod whose solidification is in process, wherein the metal rod is produced by means of casting in said at least one mould (14, 14', 14"), wherein the stirrer devices (1', 1", 1''', 1'''') are placed at a same distance with respect to each other according to a radial arrangement around the metallic material in the molten state, wherein each of the stirrer devices (1', 1", 1''', 1'''') is provided with at least two induction coils (20', 20", 20''') made of windings, the coils (20', 20", 20''') of each of the stirrer devices (1', 1", 1"', 1'''') being placed in line one after the other along a longitudinal development axis of the electromagnetic stirrer device according to a configuration in which the windings of the coils (20', 20", 20''') are placed on one single plane which is parallel to the longitudinal development axis of the respective stirrer device, the coils (20', 20", 20''') being configured and structured in such a way as to generate an electromagnetic field of application of a stirring force on the metallic material in the molten state characterised in that the control method comprises at least one phase of switching between two operating configurations of the electromagnetic stirrer devices (1', 1", 1''', 1'''') namely a rotary stirrer and a linear stirrer on a same casting machine of which: - a first operating configuration in which at least one of the coils (20', 20", 20''') of a first stirrer device of said stirrer devices (1', 1", 1''', 1'''') is controlled in a coordinated way with corresponding others of said coils (20', 20", 20''') of the others of said stirrer devices (1", 1''', 1'''') in such a way that the reciprocally coordinated coils (20', 20", 20''') generate a rotating electromagnetic field inducing in the metallic material in the molten state a rotational motion on a rotational plane which is orthogonal with respect to a direction of extraction of the metal rod from the mould (14, 14', 14"); - a second operating configuration in which at least two of the coils (20', 20", 20''') of said stirrer devices (1', 1", 1''', 1'''') are controlled in a reciprocally coordinated way with respect to each other in such a way that the reciprocally coordinated coils (20', 20", 20''') generate a linear electromagnetic field inducing in the metallic material in the molten state a linear motion according to a direction which is parallel to the longitudinal development axis of the respective stirrer device; and further characterised in that the first operating configuration is obtained by means of a series of sub-phases of driving of the reciprocally coordinated coils (20', 20", 20''') in which each sub-phase of driving is a phase of supply of one of said reciprocally coordinated coils (20', 20", 20''') by means of a driving current supplied by a respective inverter (2', 2", 2''', 2'''') between a driving branch of the respective coil (20', 20", 20''') and a compensation branch of the inverter which is connected to a common star point of the coils (20', 20", 20''') of the same stirrer device (1', 1", 1''', 1''''), the combination of said sub-phases of driving of the reciprocally coordinated coils (20', 20", 20''') being such that the driving current supplied in a first sub-phase to one of said reciprocally coordinated coils (20', 20", 20''') is phase-shifted with respect to the driving current supplied to another one of said reciprocally coordinated coils (20', 20", 20''') in a second sub-phase which is subsequent to the first sub-phase. - a first operating configuration in which at least one of the coils (20', 20", 20''') of a first stirrer device of said stirrer devices (1', 1", 1''', 1'''') is controlled in a coordinated way with corresponding others of said coils (20', 20", 20''') of the others of said stirrer devices (1", 1''', 1'''') in such a way that the reciprocally coordinated coils (20', 20", 20''') generate a rotating electromagnetic field inducing in the metallic material in the molten state a rotational motion on a rotational plane which is orthogonal with respect to a direction of extraction of the metal rod from the mould (14, 14', 14"); - a second operating configuration in which at least two of the coils (20', 20", 20''') of said stirrer devices (1', 1", 1''', 1'''') are controlled in a reciprocally coordinated way with respect to each other in such a way that the reciprocally coordinated coils (20', 20", 20''') generate a linear electromagnetic field inducing in the metallic material in the molten state a linear motion according to a direction which is parallel to the longitudinal development axis of the respective stirrer device;