"Dirgahayu" (Perpetuity) is a duet single by Malaysian artists, Faizal Tahir and Siti Nurhaliza, released on 12 August 2016. It was released to serve as a theme song for a 100-episode Malaysian television series, Lara Aishah. Co-written by Faizal himself, it was recorded in July 2016 before it was released a month later.

On 22 August 2016, a lyric video for the song featuring clips from Lara Aishah was published on Faizal's official YouTube account. This song was later included as a bonus track on Faizal's fourth studio album, (Anatomy) which was released on 4 November 2016. It was performed live by the duo at the 22nd Anugerah Industri Muzik on 18 December 2016 with its official music video premiering in the background as the backdrop for the live performance. On 19 December 2016, "Dirgahayu"'s music video was uploaded and published on YouTube.

The news about the recording arose when Faizal Tahir talked about it at his iAMFAITHMEN's Eid al-Fitr open house at The Gardens in Mid Valley on 20 July 2016. Originally meant to be mentioned briefly in the interview, Faizal decided to tell the media all about his project with Siti Nurhaliza. During the interview, he revealed that the song just finished recording a week before.

The whole duet project began when he was approached by Datin Zaiton Mohamad Jiwa, owner of Global Station. She offered him a chance to produce and record a duet with Siti Nurhaliza for her production house's latest television series, Lara Aishah. Upon receiving the offer, Faizal immediately worked on the song during the Islamic month of Ramadan. Siti and Faizal recorded their vocals separately since at the time of Faizal's recording, Siti was in Mecca to perform the Umrah. Fully composed by Mike Chan, Ezra Kong, and Faizal himself, Faizal recorded his part during Ramadan while Siti recorded her part after Eid al-Fitr. Faizal commented: "Dirgahayu is fully composed by myself and two friends of mine which are Mike Chan and Ezra Kong. Actually, before this people have been asking for Datuk Siti Nurhaliza and I to work together. By happenstance, the production company, Global Station Pte Ltd proposed to me to compose a song with her for a 100-episode drama series for Astro."

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