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25 SOUND AND VIBRATION/JANUARY 2004 estimates a so-called common-denominator transfer function model. 8 It was found that these “initial values” already yielded very accurate modal parameters with a very small computational effort. 7, 9, 10 The most important advantage of the LSCF estimator over available and widely applied parameter estimation techniques2 is the fact that very clear stabilization diagrams are obtained. Further analysis and background information are available in the references. 10, 11 It was found that the identified common-denominator model closely fit the measured frequency response function (FRF) data. However, when converting this model to a modal model by reducing the residues to a rank-one matrix using Singular Value Decomposition (SVD), the quality of the fit decreased. 9 Another feature of the common-denominator implementation is that the stabilization diagram can only be constructed using pole information (eigenfrequencies and damping ratios). Neither participation factors nor mode shapes are available initially. 12 The theoretically associated drawback is that closely spaced poles will erroneously show up as a single pole. These factors provided motivation for a polyreference version of the LSCF method, using a so-called right matrix-fraction model. In this approach, the participation factors are also available when constructing the stabilization diagram. The main benefits of the polyreference method are that the SVD step to decompose the residues can be avoided and closely spaced poles can be separated. 12-13 Here we briefly review the theory.