Rav Shach zt”l said, he heard this story from the Strikover Rebbe zt”l :
A Stoliner Chosid came to the Tchortkover Rebbe zt”l and asked him permission to daven loud (Minhag Stolin).
The Rebbe said to him, the Minhag in Tchortkov is not to daven aloud.
He quoted to him Maamorei Chazal that are against loud Davening, and forbade him to be Meshane the Minhag Hamkom.
The Stoliner Chosid came to Shul . He managed to hold himself back and davened the whole Pesukei Dezmria quietly.
By the time he reached Nishmas, he couldn’t hold himself back and started screaming on top of his lungs “Nishmas Kol Chai !!!!“.
After the Davening, the Chosid went over to the Rebbe and wanted to apologize. Before he got a chance to open his mouth the Rebbe told him how beautiful his Nishmas was, how he enjoyed the loud Davening.
The Chosid was flabbergasted, didn’t the Rebbe say that it is wrong to daven aloud in his Shul.
The Rebbe explained to him, ” If you come and ask on Wednesday to change on Shabbos the Minhag Hamokom , then the answer is, it is wrong to do so.
However if during davening you can’t control yourself , you get so excited with your davening ,then those are the most inspiring and beautiful Tefilos