Yes you get the results of the music scholarship before you complete the CAF.
It indicates if your score is high enough to be pretty much guaranteed a place on offer day.
Having sat a lot of music scholarships, KFS has the most comprehensive one of any state school.
There is an MAT test, aural tests, opportunity to play 2 pieces on one or more instruments, mini-interview and option to do an additional sight-reading test.
To compare with a few other schools:
WLFS - 5 minute aural test.
Haberdashers - a long MAT test from which the top 80 are invited back for an interview, performance of 2 pieces and an aural test.
Camden Girls - a very long MAT test from which the top 50 are invited back. Top 2 MAT scores get automatic scholarship, another 8 (?) are awarded based on scores from performance and interview.
KFS give all applicants the chance to do everything. There is also likely to be a high correlation between aptitude and high skill level. DD was already G6/7 level in her first study and G3 in her second in Y6. She's now added another 3 instruments and was performing in public with one within 3 months of even picking it up for the first time. KFS is also one of the few that doesn't have an obvious preference for only classical or orchestral (unlike quite a few of the others).