Egyptian pop star Amr Diab surprised fans everywhere when he recently released the music video for his new single "Al-Qahira" (Cairo), revealing that iconic Egyptian singer Mohamed Mounir collaborated with him on the song.

Given the reigning status of the music giants who are considered to be the two top artists in Arabic music, their first-ever collaboration quickly went viral on social media. The music video got more than half a million views in two days.

Diab released a teaser for the song last November, as well as a short teaser for the music video in late January, but neither of them mentioned or showed that Mounir had collaborated with him on the song and video.

However, Diab shared a photo of him and Mounir inside a recording studio on his social media platforms at the end of November, without mentioning exactly what they were working on.

The photo left both of their devoted fans, who refer to them in Arabic as "the highland" and "the king" respectively, wondering about the highly anticipated collaboration, not knowing that it was "Al-Qahira."

The song, which is Diab's first single off his upcoming album that will be released later this year, is an ode to the city of Cairo. It was written by Tamer Hussien, composed by Diab and Ahmed Hussien and arranged by Osama El-Hendy.

The music video, which was produced by Nay for Media and directed by Dr. Sherif Sabry, features sweeping cityscape views of Egypt's capital, as well as Diab and Mounir singing together by Cairo's Nile.

Over the course of their almost four decades-long careers, Diab and Mounir have cemented their respected places in the history of Arabic music as the two modern Arab musical legends.

Although the two have taken very different routes with their artistry, both have innovated musical styles unique to them.

Diab became the best-selling Middle Eastern artist through blending Oriental and Mediterranean music with Western pop sounds. Mounir, who also recently released new music which went viral, became the most acclaimed Arab artist of his time through combining classical Arabic and Nubian music with Western jazz, reggae and soul music.