In Venetic inscription no. 249, Ethnographic Museum of Vienna, the r in the second line goes with tola in the first and tolar is a verb, third singular present middle, and not a noun. It belongs with OIr. canar and has an indicative and personal meaning ‘he dedicates’. canar means in the Old Irish glosses ‘is sung’, not ‘there shall be singing’. The comparison of Old Irish, Latin, Oscan ( fufans ), Venetic, Greek ( ἔτλᾱν ), Lithuanian, Old Ch. Slav., and perhaps Tocharian, indicates that this ā -formation in PIE was essentially indicative. Its ‘injunctive’ value is simply a modal use of the indicative.
Edith Frances Claflin (Sun,) studied this question.