As a result of Ant's answer to my question, I have found the answer for me; when using Set List Maker, I was recording in Logic Pro, saving to iTunes and Set List Maker would use the track from iTunes. Some of the tracks I recorded years ago, before the advantage of modern apps, and it was they that would not Airdrop. By default, I discovered that if I 'dragged' the track from iTunes into a Logic Pro 'audio track' and titled it, I could then Airdrop into STXX; in case this helps anyone! Mick