"APT." by ROSÉ and Bruno Mars is a heartfelt duet that explores the emotional aftermath of a love that has faded. Set against the backdrop of an empty apartment, the song reflects on the memories that linger long after the relationship has ended. ROSÉ's delicate, soulful voice intertwines with Bruno Mars' smooth, rich vocals as they both express the pain of lost love. Their harmonies highlight the deep sense of nostalgia and longing for what was once cherished. The apartment, though physically unchanged, becomes a symbol of a love that once filled it, now haunting with emptiness.