* Bass guitar: The bass guitar provides a low-end foundation for the song. The bass line is simple but effective, and it helps to create a sense of groove.
* Electric guitar: The electric guitar is used to create the song's main melody. The guitar riff is catchy and memorable, and it helps to create the song's overall mood.
* Synthesizer: The synthesizer is used to create a variety of sounds in the song, including the arpeggiated chords that play in the background. The synthesizer also helps to create the song's overall atmosphere.
* Vocals: The vocals are the most important element of Heartless. Weeknd's voice is soulful and expressive, and he delivers the song's lyrics with conviction. The vocals are mixed perfectly with the other instruments, and they create a truly unforgettable listening experience.