According to Chaudenson (1974: 372) ansanm can also function as instrumental (Li la rouv la port ansanm en vye kle. 'He opened the door with an old key.'). However, this function is not attested in my corpora.
Source: Barat et al. 1977: 54
Source: Chaudenson 1974: 372
Source: Cellier 1982: 52