A method of controlling an ultrasonic surgical tool by a console to reduce presence of a harmonic signal , the method comprising: driving the ultrasonic surgical tool with a first drive signal applied by the console ; acquiring characteristics of the harmonic signal resulting from driving the ultrasonic surgical tool with the first drive signal by the console , the characteristics being at least a frequency and a phase of the harmonic signal , by: generating current and voltage samples relating to the first drive signal , wherein the characteristics of the harmonic signal are present in the generated current and voltage samples, monitoring the harmonic signal with the generated current and voltage samples and increasing a mechanical current to the ultrasonic surgical tool until the harmonic signal reaches a predetermined level, and acquiring the characteristics of the harmonic signal responsive to the harmonic signal reaching the predetermined level; generating a cancellation signal with a frequency similar to the acquired frequency of the harmonic signal and a phase that is shifted in relation to the acquired phase of the harmonic signal by the console ; combining by the console the first drive signal and the cancellation signal to produce a second drive signal , the second drive signal being sinusoidal; and driving the ultrasonic surgical tool with the second drive signal applied by the console such that presence of the harmonic signal resulting from driving the ultrasonic surgical tool with the second drive signal is reduced relative to presence of the harmonic signal resulting from driving the ultrasonic surgical tool with the first drive signal . driving the ultrasonic surgical tool with a first drive signal applied by the console ; acquiring characteristics of the harmonic signal resulting from driving the ultrasonic surgical tool with the first drive signal by the console , the characteristics being at least a frequency and a phase of the harmonic signal , by: generating current and voltage samples relating to the first drive signal , wherein the characteristics of the harmonic signal are present in the generated current and voltage samples, monitoring the harmonic signal with the generated current and voltage samples and increasing a mechanical current to the ultrasonic surgical tool until the harmonic signal reaches a predetermined level, and acquiring the characteristics of the harmonic signal responsive to the harmonic signal reaching the predetermined level; generating current and voltage samples relating to the first drive signal , wherein the characteristics of the harmonic signal are present in the generated current and voltage samples, monitoring the harmonic signal with the generated current and voltage samples and increasing a mechanical current to the ultrasonic surgical tool until the harmonic signal reaches a predetermined level, and acquiring the characteristics of the harmonic signal responsive to the harmonic signal reaching the predetermined level; generating a cancellation signal with a frequency similar to the acquired frequency of the harmonic signal and a phase that is shifted in relation to the acquired phase of the harmonic signal by the console ; combining by the console the first drive signal and the cancellation signal to produce a second drive signal , the second drive signal being sinusoidal; and driving the ultrasonic surgical tool with the second drive signal applied by the console such that presence of the harmonic signal resulting from driving the ultrasonic surgical tool with the second drive signal is reduced relative to presence of the harmonic signal resulting from driving the ultrasonic surgical tool with the first drive signal . <EOS>