How to pronounce 疊字 in Cantonese (3 out of 4):

只有疊字先需要變調
It's just a change of tone.

Cantonese Sentence Breakdown

只有 zi2 jau5
only
疊字 dip6 zi6
reduplication; reiterative locution; repetition of characters
sin3
early
prior
former
in advance
first
for now
ancestor
pioneering
only then
需要 seoi1 jiu3
need
變調 bin3 diu6
change tone (in speech or singing)