2x interviews
Interview 1: discussion of set material; Interview 2: personal interests, own compositions
Reading biographies of composers
Try to show that you have original ideas
Remember this advice isn't official. There is no guarantee it will reflect your experience because university applications can change between years. Check the official Cambridge and Oxford websites for more accurate information on this year's application format and the required tests.
Also, someone else's experience may not reflect your own. Most interviews are more like conversations than tests and like, any conversation, they are quite interactive.
Test taken: None
Number of interviews: 2
Time between interviews: 6 hours
Length of interviews: 30 mins
Online interview: No
One interview was academic and about set material given to me 30 mins before. The other was about me, about my taste, about my own work as a musician. I'm a composer so we talked about my recent compositions.
Reading the biographies of composers in which I was interested, using musical encylopedia and dictionaries (Oxford Comanion to Music and Cambridge Guide to Music) to clear up my basic understanding of concepts including forms/ structures/modes/ insrtuments/composers/genre/and periods. The point was not to gain an in-depth knowlage but instead use them as a kind of dummies guide, so that I could apply these new concepts to the areas in which my knowledge was aleady more extensive.
Also, read (and make notes on) papers! Maybe one, and if you can, more. The reason I give this advice is that reading something like a high-brow academic paper widend my year 13 understanding of the subject significantly; although I may not have understood all of it, maybe not even the majority of it, once I returned to reading a more easy-going text, I was far better placed to judge what interested me and what didn't. I got a sense of what bits of information were relevant and useful to me personally and what wasn't. In terms of papers to read, I would suggest reading on a subject area of which you know little but that may have occurred to you in the past as potentially interesting. Trialling JSTOR or Google Scholar is a good place to start.
Be confident! Very few people ace their interview. Cambridge is really intimidating to an outsider, but remember that everyone is pretty friendly in reality. I'd also say that there are a lot of posh - or at least very 'well spoken' types here, and many more at the intereviews. I found this intimidating, something about the upper middle class mannerisms seemed at the time to make all these people seem incredibly clever - geniuses even. But really it's just how they've grown up talking and has little to nothing to do with their congnitive power.
The thing is, the intereviews will know more about what you're talking about than you do - it's like if you were tutoring a Year 9 student, you obviously know more than them, but it doesn't mean that the Year 9 student can't still impress you with their knowledge or an original perspective on things, and this is essentially what intereviewers want. It's got little to do with how you speak, not even that much to do with your vocab (although you do need a faily good vocab when it comes to your specialism), it's about your ideas, and about how you can show that you have original ideas while at the same time thinking about what infomation you have been provided with and what other perspectives there are.