Here's something I've never seen in "real life", timing sheets for a composer.
This is from a Fred Quimby-produced Hanna/Barbera Tom and Jerry cartoon "Heavenly Puss" with music by Scott Bradley.
This taken from "Film Music: A Neglected Art" by Roy M. Prendergast.
The top cell is the director's note for action. "Scene of hell shot (unintelligible) l[ight] Red filter. Blast of Flame from crater."
The narrow "sound" row contains numbers: 24...8. 24...8. 8...24. I assume these are frame counts. That makes 32 frames per bar. Four counts of 8.
Also the directors' "Phoom". This syncs with bursts of flame.
The section which the sheets refer to happens around the four minute mark.
Today, if you're doing a commercial project the director might not even talk to the composer. In almost ever other case the music is done in post-production. The "right" way to do it, of course, is to record the music first and animate to the soundtrack.
Given the production schedule of these classic shorts, the work needed to overlap. These sheets are an exacting means of communication that allow for quick work flow.