A poet in South India by name Poyamoli Pulavar in his early days had intense devotion for Lord Siva. Due to the intensity of his love to Lord Siva, he refused to bow to, or sing the glory of, any other deity including Lord Shanmukha. The Lord gave him the vision and showed him the unity of the forms of Siva and Shanmukha. Thereafter, Poyamoli Pulavar developed greater love and sincerity of devotion to Lord Shanmukha, and he became known as Siva Kavi.
Sivananda, Swami. Lord Shanmukha and His Worship. World Wide Web edition. India: Divine Life Society, 2000.