@celesteh Not fully correct.
First, you'd only need a new opt-in, if people you were contacting weren't ever subscribing, i.e. if there was no prior opt-in, or one that is incompatible with the GDPR.
Second, consent is one of several cases in which the data processing is legal. There are other legal terms such as contract, legitimate interest etc. that could apply.
Third, there is certainly a gray area when it comes to the network of your fellow artists. E.g., they could be personal contacts.
@celesteh That is to say, I think in this case, what is more important is that people do state that you are in their contact lists, that they are aware of the privacy issue and acertain that they won't use the data otherwise, and that they are happy to take you off the communications with a very simple action, even if it's not the strictly required opt-in.