A key benefit in intelligent Computer Assisted Language Learning (iCALL) is that it allows complex linguistic phenomena to be incorporated into digital learning platforms, either for the autonomous learner or to complement classroom teaching. The present paper describes (1) complex phonological/ morphophonemic alternations of Irish, which are problematic for many learners; (2) an iCALL platform, "An Scéalaí," which uses speech technology and Natural Language Processing (NLP) prompts to train writing and aural skills -- in this paper the target is the morphophonemic alternations of (1); and (3) a perception experiment to guide how the platform might be used for prompt-based self-correction. The perception experiment has been carried out using newly built synthetic voices based on deep neural network technology. [For the complete proceedings, see ED600837.]