We present data on the pronunciation of oral and nasal vowels in northern and southern French varieties. In particular a sharp contrast exists in the fronting of the open /O/ towards [œ] in the North and the denasalisation of nasal vowels in the South. We examine how linguistic changes in progress may affect these vowels, which are governed by the left/right context and bring to light differences between reading and spontaneous speech. This study was made possible by automatic phoneme alignment on a large corpus of over 100 speakers.