The King Black Dragon Lair was previously located in the Temple of Ikov next to the icy area where the track unlocks. When it was moved, music was unlocked by map tiles in those days. As such, being able to unlock the music in the Temple of Ikov is likely an oversight by Jagex.
^Jagex. Mod Ash's Twitter account. 7 August 2014. Mod Ash: "When RuneScape 2 came out, the KBD lair was mapped by the Temple of Ikov. It changed due to safe-spotting."
^Jagex. Mod Ash's Twitter account. 18 February 2018. Mod Ash: "Music tracks were always based on mapsquares in those days, rather than trying to fit more neatly to irregular scenery. It would have been reasonable for the devs to move the track as well as the dragon (though the original cave was still there last I saw) but it's no biggie."