DD sat around 8 music scholarship/aptitude tests 2 years ago.
There's a huge difference in what different schools ask you to do - and in what is on offer if you are successful.
The most basic one just asked for aural tests, clapping in time etc. Did not want any information at all about instruments/grades or anything like that. Gaining a music place just got you a school place.
The most comprehensive had a full written Musical Aptitude Test, aural tests, performance (two contrasting pieces on either one instrument or two) and an interview. Gaining the full scholarship and a top 15 ranking got you a guaranteed place at the school, free tuition on one instrument, free music theory lessons, masterclasses and concert trips.
The others all fell somewhere between the two.
There were several hundred sitting at 3 of the schools. (All London schools).
DD doesn't do exams, and choose to only go with voice for all (but offered to play the piano if they wanted). She would have been around G6 level at the time.
Feel free to PM me if you are interested in specific schools and if we sat theirs I'll give you the details from what I remember.
And yes, you definitely have to put it on the CAF. DD got a guaranteed place at the one she really wanted so we put that down as first choice... still didn't relax until I got the confirmation though! The schools were all very good at getting results back before forms had to be submitted.