The dynamics of the human middle ear (ME) has been studied in the past using several computational and experimental approaches in order to observe the effect on hearing of different conditions, such as conductive disease, corrective surgery or implantation of a middle ear prosthesis. Multi-body (MB) models combine the analysis of flexible structures with rigid body dynamics, involving fewer degrees of freedom than finite element (FE) models, but a more detailed description than traditional 1-D lumped parameter (LP) models. This study describes the reduction of a reference FE model of the human middle ear to a MB model and compares the results obtained considering different levels of model simplification. All models are compared by means of the frequency response of the stapes velocity vs. sound pressure at the tympanic membrane, as well as the system natural frequencies and mode shapes. It can be seen that the flexibility of the ossicles has a limited impact on the system FRF and modes, and the stiffness of the tendons and ligaments only plays a role when above certain levels. On the other hand, the restriction of the stapes footplate movement to a piston-like behavior can considerably affect the vibrational modes, while constrains to the incudomalleolar and incudostapedial joints can have a strong impact on the system FRF.