Past perfect simple

We use the past perfect simple
– When we are talking about the past and want to mention something that happened earlier:
1. His father was a composer and his grandfather had also been a musician. (Mozart’s grandfather was a musician and then later his father became a composer)

Sometimes we use words like just or already. Notice that these adverbs go between the auxiliary and the main verb:
2. By the time he was 17, Mozart’s reputation had already begun to spread through Europe.

-We use the simple past tense if the events are mentioned in chronological order:
3. His grandfather was a musician and his father was also a composer.

with words like when, as soon as, by the time, and after to show the order of events:
4. When Mozart was born, five of his siblings had already died. (Mozart’s siblings died first, then Mozart was born)

Notice the difference in meaning between these two sentences:
5. When I got home, my husband cooked dinner. (= I got home and then my husband cooked dinner)

6. When I got home, my husband had cooked dinner. (= my husband cooked dinner before I got home)

-to talk about an indefinite time before a particular point in the past, often with words like always, sometimes, never, before, by + fixed time:
7. His family was richer than they had ever been before. (= they were not as rich at any time before this point in the past)
8. By the time he was six, the little boy had written a composition of his own.

-to report past events using reporting verbs :
9. The man told me he had met my father a long time before.