There are two pieces of mourning that enter Shul on Shabbos Chazon in Ashkenazi shuls:
- Lecha Dodi is sung to the tune of “Eli Tzion”, the concluding Kinah of Tisha B’Av morning.
- The Haftora is read to the trop tune of Eicha.
These two exceptions make some poskim uncomfortable with the premise I stated, that there is no churban on Shabbos. But I think there is value to these two minhagim in particular, and we should not extend them to other parts of Shabbos.
Why these two? Because both Lecha Dodi and the minhag of Haftora are already Golus-emphasizing practices. Read a certain way, Lecha Dodi is practically a Tisha B’Av Kina already! Read it again if you don’t believe me.
And a quick read of the brochos after the Haftora reveals that it too is a Golus-minded mitzvah. It was founded at a time of persecution, when oppressors forbade reading the Torah in public. And as such, it is placed in a context of asking Hashem to bring the Geula, Eliyahu Hanavi and Moshiach ben David. So it’s also a pseudo-Kina as well.
I surmise that minhag Yisrael allowed for these two musical choices to allow us to be aware of Golus because they make us aware, non-verbally, of how there is a form of Golus even on Shabbos.