Ganga and the Holy Trinity - Brahma, Vishnu, Mahesh
There was a time when Ganga suddenly became associated with the Holy Trinity. Sage Narada, the son of Brahma, was very fond of singing, but his singing was not correct. As a result, the ragas (combinations of musical notes evoking certain moods) suffered inexplicable torment. When Narada understood the reason for the ragasqual, he promised to sing only if he had learned it properly. But the torment of the ragas had to be cured and so a musical concert by a master musician had to be arranged. Except Bhairav, who could be a better musician; So Narada approached Mahesh to sing the ragas...

Ganga and the Holy Trinity - Brahma, Vishnu, Mahesh
There was a time when Ganga suddenly became associated with the Holy Trinity.
Sage Narada, the son of Brahma, was very fond of singing, but his singing was not correct. As a result, the ragas (combinations of musical notes evoking certain moods) suffered inexplicable torment. When Narada understood the reason for the ragasqual, he promised to sing only if he had learned it properly. But the torment of the ragas had to be cured and so a musical concert by a master musician had to be arranged.
Except Bhairav, who could be a better musician; Therefore, Narada approached Mahesh to sing the ragas and heal. Shiva agreed but on the condition that Vishnu and Brahma should listen to his concert as a master musician needed master listeners. Both Vishnu and Brahma rejoiced at the opportunity to hear Bhairav sing and readily agreed.
At the first note of the concert, the ragas began to heal and soon they were all healed. So deep and soothing was Shiva's musical rendition that Vishnu was transported into a rapture of divine joy and actually began to melt. Now Brahma collected the water emanating from the melting Vishnu in his Kamandalu. After the concert, Brahma created Ganga from this water. Since her birth was under the most favorable circumstances and was made from the water that emanated from the melting of Vishnu, Ganga was given by birth the power to purify everything that came in contact with her.