Complex sentence: In the early days the studios were mainly used by Dutch artists, but later also international musicians such as Elton John, Scorpions, Def Leppard, Iron Maiden, Tina Turner, and U2 used the facilities.
Split into simpler sentences: In the early days the studios were mainly used by Dutch artists. Later, international musicians such as Elton John, Scorpions, Def Leppard, Iron Maiden, Tina Turner, and U2 have used the facilities.