What does the phrase " on the part of chance" mean?

And here's the whole statement:
"On the other hand, you do not believe in alliterative rhymes as I do,
I am of the opinion
that Mozart, Mendelssohn, and Meyebeer, that Bach, Beethoven, and
Brahms do not
alliterate with one another without an inderstandong pn the part of
chance"

I don't quiet understand the meaning of this passage, either. Does it
mean to say
that these two groups of composers actually don't correlate with one
another except their
the starting letter of their names?
.