Which sentence should i use?

Question

"He had perfect pitch and discovered that with his whistle he could hack the phone system."

"He had perfect pitch, and he discovered that with his whistle he could hack the phone system."

Answer 1

Well, either is grammatically correct. I would try reading it aloud within the passage to see which flows the way you want it to.

Answer 2

Both are grammatically correct, so you should consider additional context like paragraph flow and sentence variety.