Here’s the correct matching for British and American musical traditions based on your list:
George Gershwin - E (is an American composer who wrote both classical music and popular tunes.)
The Edinburgh festival - F (is an annual holiday of music and drama.)
Wales - G (is famous for its choral music.)
Benjamin Britten - D (is a famous British composer who wrote the first British national opera.)
Henry Purcell - C (is a famous British composer and pianist who wrote symphony, choral music and music for children.)
Rock and roll - H (is an American composer who wrote rock music.)
Elvis Presley - G (was called the King of rock'n'roll.)
The Beatles - I (are the most popular British rock group.)
Elton John - B (is a brilliant rock composer and singer.)
Promenade concerts - K (were started to teach young people to listen to classical music.)
So the final matches are:
1 - E 2 - F 3 - G 4 - D 5 - C 6 - H 7 - G 8 - I 9 - B 10 - K