I am trying to understand why in a progression in C# major there is an A major chord, the chords are to be precise: C# Bbm F# A, where did this A come from?
I thought it might be a secondary dominant that does not resolve but still, A would resolve on a D which is not present in the C# scale, so why does it fit in this key?
The song is "gua10" by "tha Supreme & Lazza", the chords in question are the first four at the beginning of the song and are repeated throughout, the song is in the key of C# major.