The main goal of this thesis is to study the process of vowel harmony in Valencian Catalan using the methodology and tools provided by laboratory phonology. It intends to illustrate the formant patterns of stressed and unstressed vowels that are involved in the assimilation process. Four samples that represent different Valencian varieties have been selected for this purpose. A secondary goal of the thesis is to compile previous findings in the literature about the extent of the harmonic phenomenon in Valencian varieties in order to compare their results with ours, as well as to review the orthoepic assessment of the assimilation process in prescriptive works from academic institutions. The study is divided in four main sections. In the first one, we study the harmonic phenomenon in a general way, drawing mainly from formal phonologic studies, in order to place the Valencian harmonic process amongst the models described by phonological theories. In the second section, we revise the geographic distribution of the harmonic patterns in the traditionally Valencian-speaking areas of the Valencian Community, using data obtained through field research. We also carry out a revision of the normative and orthoepic considerations that the assimilation process has received in the prescriptive guidelines. In the third section, we provide a detailed description of the methodological decisions that guide the acoustic study conducted, using a set of controlled oral samples. In the last part, we analyse and interpret the acoustic data that allow us to track the phonetic bases of the phonological process. The analysis includes not only the environments that have been canonically described in the literature, i. e., two contiguous syllables in any given word, but also other prosodically and morphologically controlled structures that allow us to achieve a more complete view of the phonological features that describe the harmonic phenomenon in Valencian. The results of the instrumental analysis confirmed the existence of three models of vowel harmony in the Valencian language: a prototypical model in which the two stressed open-mid vowels trigger the assimilation of the low vowel /a/, and two models limited to a single vowel, /ɛ́/ or /ɔ́/, as triggers for the spreading of the colour features [front] and [round], respectively. Formant frequency values revealed that there are no differences of height or colour between the stressed vowels of the harmonic and non-harmonic varieties. Furthermore, the study of different phonological environments allowed us to define a metrically conditioned domain for the assimilation process, which operates on the low post-tonic vowels that define, together with the preceding stressed vowel, the main foot. We end up identifying that the colour features can spread through the prosodic word, thus surpassing word morphological boundaries as long as the vowels involved (/ɛ́, ɔ́/ and /a/) are grouped within the basic rhythmic category of the main foot. Hence, we have been able to determine that, in addition to the low vowels of prototypical environments such as tela and cosa, the colour features of the stressed open-mid vowels can also extend to the final post-tonic vowels of prosodic words such as perd-la and dissol-la, as well as to the non-final post-tonic vowels of serra-la and toca-la. On the contrary, vocalic segments that are outside the main foot, such as the final post-tonic vowels of serra-la and toca-la, as well as those of the feminine article in sequences such as perd la clau and dissol la farina, maintain a relatively centralized low vowel, lacking the colour features that characterize the target vowels of Valencian vowel harmony. The results additionally suggest that Valencian vowel harmony, especially in the environment defined by the presence of a round stressed vowel /ɔ́/, might respond to a phonological reinterpretation of a previous coarticulatory process involving the mid-open stressed vowels (which are notably open in Valencian) and the post-tonic low vowel (which is a segment of the unstressed vowel subsystem characterised in Western Catalan as being particularly mobile in the horizontal and vertical axes).
