Processor for processing an audio signal, comprising: an analyzer for deriving a window control signal from the audio signal, the window control signal indicating a change from a first asymmetric window to a second window, wherein the second window is shorter than the first asymmetric window, or the window control signal indicating a change from a third window to a fourth asymmetric window, wherein the third window is shorter than the fourth asymmetric window; a window constructor for constructing the second window using a first overlap portion of the first asymmetric window, wherein the window constructor is configured to determine a first overlap portion of the second window using a truncated first overlap portion of the first asymmetric window and to determine a second overlap portion of the second window corresponding to a first overlap portion of a further window following the second window, or for constructing the third window using a second overlap portion of the fourth asymmetric window, wherein the window constructor is configured to determine a first overlap portion of the third window corresponding to a second overlap portion of a further window preceding the third window and to calculate a second overlap portion of the third window using a truncated second overlap portion of the fourth asymmetric window; and a windower for applying the first asymmetric window and the second window or the third window and the fourth asymmetric window to obtain windowed audio signal portions. an analyzer for deriving a window control signal from the audio signal, the window control signal indicating a change from a first asymmetric window to a second window, wherein the second window is shorter than the first asymmetric window, or the window control signal indicating a change from a third window to a fourth asymmetric window, wherein the third window is shorter than the fourth asymmetric window; the window control signal indicating a change from a first asymmetric window to a second window, wherein the second window is shorter than the first asymmetric window, or the window control signal indicating a change from a third window to a fourth asymmetric window, wherein the third window is shorter than the fourth asymmetric window; a window constructor for constructing the second window using a first overlap portion of the first asymmetric window, wherein the window constructor is configured to determine a first overlap portion of the second window using a truncated first overlap portion of the first asymmetric window and to determine a second overlap portion of the second window corresponding to a first overlap portion of a further window following the second window, or for constructing the third window using a second overlap portion of the fourth asymmetric window, wherein the window constructor is configured to determine a first overlap portion of the third window corresponding to a second overlap portion of a further window preceding the third window and to calculate a second overlap portion of the third window using a truncated second overlap portion of the fourth asymmetric window; and a windower for applying the first asymmetric window and the second window or the third window and the fourth asymmetric window to obtain windowed audio signal portions. for constructing the second window using a first overlap portion of the first asymmetric window, wherein the window constructor is configured to determine a first overlap portion of the second window using a truncated first overlap portion of the first asymmetric window and to determine a second overlap portion of the second window corresponding to a first overlap portion of a further window following the second window, or for constructing the third window using a second overlap portion of the fourth asymmetric window, wherein the window constructor is configured to determine a first overlap portion of the third window corresponding to a second overlap portion of a further window preceding the third window and to calculate a second overlap portion of the third window using a truncated second overlap portion of the fourth asymmetric window; and a windower for applying the first asymmetric window and the second window or the third window and the fourth asymmetric window to obtain windowed audio signal portions.