Барабан задавал ритм, а флейта делала мелодию легче.

The drum set the rhythm, and the flute made the melody lighter.

Breakdown of Барабан задавал ритм, а флейта делала мелодию легче.

• мелодия: the melody
• делать: to make
• а: and
• ритм: the rhythm

Questions & Answers about Барабан задавал ритм, а флейта делала мелодию легче.

Why is there a comma before а?

Because а is joining two separate clauses here:

• Барабан задавал ритм
• а флейта делала мелодию легче

Each part has its own subject and verb, so Russian normally puts a comma before а. This is very similar to using a comma before but in English, and often before and when two full clauses are joined.

Why is а used instead of и?

А often adds a slight contrast or comparison, not just simple addition.

Here the idea is something like:

• the drum was doing one musical job,
• while the flute was doing a different one.

So а highlights that contrast of roles. In English, it may still be translated as and, but in Russian а suggests whereas / while / and on the other hand more than plain и would.

Why are the verbs задавал and делала different?