Does MusicXML support roman numerals and/or functions (such as T for tonic)? I know this can be done via a workaround, namely using lyrics and a special font. But I am talking about dedicated support.
Yes for roman numerals. Maybe for functions (such as T for tonic). Look into the element Harmony in direction.mod.
The harmony elements are based on Humdrum's **harm
encoding, extended to support chord symbols in popular
music as well as functional harmony analysis in classical
The harmony object may be used for analysis or for
A root is a pitch name like C, D, E, where a function
is an indication like I, II, III. Root is generally
used with pop chord symbols, function with classical
functional harmony. It is an either/or choice to avoid
data inconsistency. Function requires that the key be
specified in the encoding.