UnScramble this Word: a e t s e t p l?

Questions

Domenico Scarlatti's works are often identified with "L" and a number. Whatdoes "L" stand for ?

Who wrote most of Mozart's Symphony No. 37, K. 444 ?

Although Mussorgsky wrote Pictures at an Exhibition, whose orchestration of it is usually heard ?

What is the only left handed instrument in the orchestra ?

As a choir boy, Haydn was considered a practical joker. On one occasion, he... ?