A method for controlling trajectory in a resonant marine seismic source, comprising: controlling a source frequency of the resonant marine seismic source, including: estimating a source natural frequency of the resonant marine seismic source; deriving a frequency error as a difference between the estimated source natural frequency and a frequency of the desired trajectory of the resonant marine seismic source; and driving the frequency error to zero, wherein the frequency of the desired trajectory of the resonant marine seismic source corresponds to a resonance frequency of the resonant marine seismic source when the frequency error is zero; and controlling a motion trajectory of a moving part of an oscillator (105, 130, 132) of the resonant marine seismic source after controlling the source frequency of the resonant marine seismic source to be the frequency of the desired trajectory of the resonant marine seismic source, wherein the motion trajectory of the moving part (105, 130, 132) comprises a position, a velocity, or an acceleration of the moving part of the oscillator, wherein controlling the motion trajectory of the moving part (105, 130, 132) includes: detecting the motion trajectory of the moving part of the oscillator (105, 130, 132); deriving a motion trajectory error as a difference between a desired motion trajectory of the moving part of the oscillator (105 130, 132) and the detected motion trajectory; and driving the motion trajectory error to zero, wherein the desired motion trajectory of the moving part of the oscillator (105 130, 132) corresponds to the detected motion trajectory of the moving part of the oscillator (105 130, 132) when the motion trajectory error is zero. controlling a source frequency of the resonant marine seismic source, including: estimating a source natural frequency of the resonant marine seismic source; deriving a frequency error as a difference between the estimated source natural frequency and a frequency of the desired trajectory of the resonant marine seismic source; and driving the frequency error to zero, wherein the frequency of the desired trajectory of the resonant marine seismic source corresponds to a resonance frequency of the resonant marine seismic source when the frequency error is zero; and estimating a source natural frequency of the resonant marine seismic source; deriving a frequency error as a difference between the estimated source natural frequency and a frequency of the desired trajectory of the resonant marine seismic source; and driving the frequency error to zero, wherein the frequency of the desired trajectory of the resonant marine seismic source corresponds to a resonance frequency of the resonant marine seismic source when the frequency error is zero; and controlling a motion trajectory of a moving part of an oscillator (105, 130, 132) of the resonant marine seismic source after controlling the source frequency of the resonant marine seismic source to be the frequency of the desired trajectory of the resonant marine seismic source, wherein the motion trajectory of the moving part (105, 130, 132) comprises a position, a velocity, or an acceleration of the moving part of the oscillator, wherein controlling the motion trajectory of the moving part (105, 130, 132) includes: detecting the motion trajectory of the moving part of the oscillator (105, 130, 132); deriving a motion trajectory error as a difference between a desired motion trajectory of the moving part of the oscillator (105 130, 132) and the detected motion trajectory; and driving the motion trajectory error to zero, wherein the desired motion trajectory of the moving part of the oscillator (105 130, 132) corresponds to the detected motion trajectory of the moving part of the oscillator (105 130, 132) when the motion trajectory error is zero. detecting the motion trajectory of the moving part of the oscillator (105, 130, 132); deriving a motion trajectory error as a difference between a desired motion trajectory of the moving part of the oscillator (105 130, 132) and the detected motion trajectory; and driving the motion trajectory error to zero, wherein the desired motion trajectory of the moving part of the oscillator (105 130, 132) corresponds to the detected motion trajectory of the moving part of the oscillator (105 130, 132) when the motion trajectory error is zero.