I thought 'will' is not used to mark the future tense after 'if' in English, the future being expressed in the main part of the sentence, e.g. "It will rain if Dylan sings", "sings" being in the future. So, I would translate "os bydd Dylan yn canu" as "if Dylan sings". I might be wrong, as my mother tongue is French. Can someone help me with this?
'If Dylan sings' or 'if Dylan is singing' are probably the most natural translations. The Welsh and English uses of tenses do not always match exactly.
Would "If Dylan will be singing" also be possible?
(e.g. I'm not going to the party if Dylan will be singing there)