The criteria is, I imagine, the same for anyone who’s being asked to apply a particular craft: does it fall within my capabilities? Affinities are not compulsory, rather an instinct of what the artist (or producer) is hoping to achieve. For example the difference between rhythm design for VoBR and a singer such as Susana Félix is fairly extreme in terms of approach and outcome, but if I understand what the music is about then I can apply ideas and hopefully the collaboration works out. I don’t often meet the people I work with, files are exchanged remotely, so having an affinity is a bit much to expect. I also prefer to contribute without having a conversation about expectations because either I’ll get it from listening to it, or I’m not the right person to ask. There are those that like to express concepts and grand designs but I find it incredibly superfluous to the act of feeling inspired, in fact to be more precise, in my experience ‘concepts’ sound alarm bells for a failing in either originality or craft, and can cause quite a blip in the process. Any affinities for me would come directly from the music rather than the artist, but then ‘affinities’ is too grand a word for what is essentially understanding a particular music genre and applying what you do. So in the real world, (or in the case of most collaborations these days, in the virtual world) all I need are a few audio stems, a BPM or tempo map and it’ll get done and returned electronically. To answer the last part of your question, I don’t feel regretful about past projects, they are forever what they were meant to be. There came a point when the work was deemed good enough to call complete and you signed off on it, but anything frozen in time is subject to scrutiny and criticism retrospectively, which you realise only too well at the time you’re making it, so you’re kinda geared up to living with the consequences and moving on from the outset.