Grunge fuses elements of punk rock (specifically American hardcore punk such as Black Flag) and heavy metal (especially traditional, earlier heavy metal groups such as Black Sabbath), although some bands performed with more emphasis on one or the other. Alex DiBlasi feels that indie rock was a third key source, with the most important influence coming from Sonic Youth's "free-form" noise. Grunge shares with punk a raw, lo fi sound and similar lyrical concerns, and it also used punk's haphazard and untrained approach to playing and performing. However, grunge was "deeper and darker"-sounding than punk rock and it decreased the "adrenaline"-fueled tempos of punk to a slow, "sludgy" speed, and used more dissonant harmonies. Seattle music journalist Charles R. Cross defines "grunge" as distortion-filled, down-tuned and riff-based rock that uses loud electric guitar feedback and heavy, "ponderous" bass lines to support its song melodies. Robert Loss calls grunge a melding of "violence and speed, muscularity and melody", where there is space for all people, including women musicians. "VH1" writer Dan Tucker feels that different grunge bands were influenced by different genres; that while Nirvana drew on punk, Pearl Jam was influenced by classic rock, and that "sludgy, dark, heavy bands" such as Soundgarden and Alice in Chains had a sinister metal tone.