<p>Well, the first thing to say is that probably the biggest reason my own personal collection of reference tracks is useful to me is simply that I've listened to them on (without exaggeration) hundreds of different listening systems over the last 20 years or so. Plus, during that time I've refined which references I use for what based on how useful they are, as well as continually trialling new tracks as possible additions -- in my opinion a reference collection should always be a work in progress, otherwise you're not continuing to develop your ear as an engineer. Still, various reference productions have stood the test of time for me, so I'll mention some of my favourites in a moment.</p>