In 1994, starting with the Murder was the Case soundtrack, Dre attempted to push the boundaries of G-funk further into a darker sound. In songs such as "Murder was the Case" and "Natural Born Killaz", the synthesizer pitch is higher and the drum tempo is slowed down to 91 BPM (87 BPM in the remix) to create a dark and gritty atmosphere. Percussion instruments, particularly sleigh bells, are also present. Dre's frequent collaborators from this period included Pittsburgh, Pennsylvania natives Stuart "Stu-B-Doo" Bullard, a multi-instrumentalist from the Ozanam Strings Orchestra, Sam Sneed, Stephen "Bud'da" Anderson, and percussionist Carl "Butch" Small. This style of production has been influential far beyond the West Coast. The beat for the Houston-based group Geto Boys 1996 song "Still" follows the same drum pattern as "Natural Born Killaz" and Eazy E's "Wut Would U Do" (a diss to Dre) is similar to the original "Murder was the Case" instrumental. This style of production is usually accompanied by horror and occult-themed lyrics and imagery, being crucial to the creation of horrorcore.