Complex sentence: Before this trip, Tchaikovsky had spent considerable time corresponding with Rimsky-Korsakov, Glazunov and Lyadov, and during his visit, he spent much time in the company of these men.
Split into simpler sentences: Before this trip, Tchaikovsky had spent considerable time corresponding with Rimsky-Korsakov, Glazunov and Lyadov. During his visit, Tchaikovsky spent much time in the company of these men.