Stanza's dice with the "A/I" designation are placed in an Active slot and immediately apply as soon as that Section is active.
Some A/I skills apply to Stanza's target. For these songs, you'll have to immediately choose a valid target for Stanza (adjacent, since she is Melee). Since playing songs happens at the start of Stanza's turn, this means you are forced to choose a target early. You can only have one target per turn, so you cannot choose a new target later in the turn. If you move away from your target, you then won't be able to use anything requiring a target for the rest of the turn because your selected target is no longer valid and you can't choose a new one.
Therefore, it's recommended to play these songs only once you are already adjacent to your target.