## 5 Conclusions  
Profiting from ongoing work in the collection of a new RT-MRI EP dataset for a large number of subjects, this paper presents novel analyses of vocal tract configurations, their variation during vowels production, and the synchronization of velum movement with lip aperture, for EP nasal vowels. The analyses are based in the application of GAMMs to vocal tract apertures estimated from RT-MRI images recorded at 50 fps. In general, the main objectives defined were accomplished: (1) The method adopted for dynamic analysis of RT-MRI data of the vocal tract is an evolution of recent methods based in GAMMs. (2) The applicability of such methods to nasal vowels production studies was assessed in several aspects with good results. (3) New results were produced regarding EP nasal and oral vowels production, with the novel characteristic of resulting from multi-speaker analyses. The methods explored in this article allowed us to explore, in an elegant and innovative way, data from a broad group of speakers to obtain a general model of the dynamics of the tract throughout the production of oral and nasal vowels. Although it is a first exploration, the results obtained have allowed the identification of various aspects of interest regarding the nasal vowels based on RT-MRI data for a considerable number of speakers. As shown for Brazilian Portuguese [23], we also found oropharyngeal adjustments in the low nasal vowel, giving evidence for a more raised tongue position than the oral congener. This was already taken into account by the transcription of this sound in the IPA [20]. Adjustments were also found for the mid vowels, suggesting a raised and more advanced position of the tongue in the production of the nasal congeners in a similar way as has been shown for French [17]. However, we did not find any adjustments in the high vowels, as was shown in BP [23]. This may partially explain why high nasal vowels sound less nasalized in European than in Brazilian Portuguese, but more research is needed to explore these questions. The results obtained for the 11 speakers with the proposed method corroborate previous studies reporting for \([\bar{\mathrm{i}}]\) and \([\bar{\mathrm{u}}]\) the similarity of the vocal tract configuration and its variation in time when compared to the corresponding oral vowels and a sharper difference in the configuration between \([\mathrm{a}]\) and \([\bar{\mathrm{e}}]\), which is slightly more pronounced at the end of the vowel. As previous results are generally for a speaker or a small set of speakers, this additional support for the characterization of the oral configuration for nasal vowels, the differences and similarities for the oral congeners, and the temporal organization is of paramount relevance for the advancement of description and modeling of this very relevant class of sounds for the Portuguese language, with implications in phonetics, speech therapy, and articulatory synthesis. The larger variability of the velar opening for the nasal vowel \([\bar{\mathrm{u}}]\) is one of the most interesting results obtained. We can conjecture that this variation may be associated with the proximity of the posterior part of the tongue to the velum, which will lead to less well-defined adjustments and timings. It is also possible that artifacts may be caused in the RT-MRI, image thus introducing a greater dispersion of aperture estimates. Accurate identification of the effective causes of this variation observed in \([\bar{\mathrm{u}}]\) requires further investigation. This future work to clarify the adjustments in question should, among other things, consider information on the movement of the body of the tongue in relation to the pharynx. Regarding coordination, the FLMMs showed some potential for creating possible coordination models based on a large set of speakers; the results obtained point to an anticipatory closure/minimal area of the lips with respect to velar closure.