How essential are the Trop?

How essential are the Trop?

The ta’amim (cantillation) of the Torah reading is a tradition from Moshe at Sinai; this includes both the punctuation and the trop (the tune). These guidelines were immortalized with takanas Ezra (an institution of Ezra the Scribe, from the time of the Second Temple) along with the universal weekly timetable for Krias HaTorah (the Torah reading in shul). 

Minute variations in melody developed  over time from one community to the next, and small changes reflect the character of various times of the year—for example, during the Yomim Noraim (High Holidays) and for Eichah on Tisha B’Av—though the basic tenets are all the same.

It is imperative that the Torah is read with the proper trop, or takanas Ezra is not fulfilled. The Ba’al Kriah (aka Ba’al Koreh, Torah Reader) should not mess with the original tune, even if he feels he is “improving” it. Before someone accepts the position of Ba’al Kriah, whether it is a Shabbos or weekday leining, he should be well-versed in the trop. In a minyan with no qualified Ba’al Kriah, the job must go to the most expert layman.

If there is no one available who is familiar with correct trop, halachah dictates that the Torah should nevertheless be read—but this is only a placeholder in order that the takanah of Krias HaTorah is not forgotten; the original halachic obligation has not been fulfilled. 

https://halacha2go.com?number=625

Practical Halacha: One minute a day. By Horav Yosef Yeshaya Braun, shlita, Mara D'asra and member of the Badatz of Crown Heights.