This paper compares data from different Mixtec languages to show that not all underlying tones align at the left edge of their sponsoring morpheme. This process is most thorough-going in South-eastern Nochixtlán Mixtec (MXY) where the tones of most morphemes are prohibited from aligning at the left edge. Thus for bimoraic morphemes, the underlying tones associate with the second mora, often giving rise to floating tones. The same restriction against the underlying tones aligning at the left edge also applies to monomoraic items with the result that the tone(s) sponsored by these morphemes occur as floating tones. I show that the considerable surface variation of tonal phenomena between Mixtec languages can be attributed to differences in alignment rather than differences of underlying tones. For MXY, I show that High, Mid and Low tones occur as floating tones. One outcome of this rightward shift in MXY is that stressed syllables are unspecified for tone.

Index Terms: tone, alignment, Mixtec, tone shift, stress, floating tones