The general rule is that you have the right to rescind this purchase without providing a reason within 14 days. But according to § 18 Abs 1 Z 11 FAGG the customer does not have the right to rescind for goods which are non-physical digital content if the entrepreneur has started providing the good before the 14-days-period of rescission with the explicit permit of the customer and acknowledging the loss of the right to rescind. Therefore, you confirmed when you bought the non-physical digital content that “I’m aware that I can’t cancel this purchase as soon as I open the first link to the music”. This counts as the confirmation of approval of immediate delivery and the loss of the right to rescind.
Before receiving the first link to the music you can rescind by sending an email to firstname.lastname@example.org with your contact and bank information.