Philadelphia (or Philly) soul, sometimes called the Philadelphia sound or Sweet Philly, is a genre of soul music characterized by funk influences and lush instrumental arrangements, often featuring sweeping strings and piercing horns. The subtle sound of a vibraphone can often be heard in the background of Philly soul songs. The genre laid the groundwork for disco and what are now considered quiet storm and smooth jazz by fusing the R&B rhythm sections of the 1960s with the pop vocal tradition, and featuring a slightly more pronounced jazz influence in its melodic structures and arrangements.