This operation lets you change the pitch of a sample. Pitch changing normally changes the length of the sample too (you can think of a tape machine, where the speed is altered). JAZZ however provides algorithms to change the speed without changing the length of the sample.
With the sliders you specify the amount of transposition in semitones. If the box Keep Length is checked, the transposed sample will have the same length as the original. In this case, JAZZ divides the sample into small pieces and plays these pieces with the new speed as often as necessary to match the original length. This may lead to an undesired tremolo effect if the size of the pieces is too big or too small. The slider named window size lets you adjust the size of the pieces.