The final application of music in Friday the 13th is of particular importance, as the filmmakers decided to utilize music almost exclusively for scenes and shots that showed the perspective of the killer. As such, the music comes to represent the presence of the antagonist as an anticipatory device even if the music quits during some of the actual killings. This decision is keen but also caused a few of Manfredini's more interesting recordings for the film to go unused. Only roughly five minutes of total music went unused in the picture, though, so the quantity of the dropped material is not significant. The composer did his best to provide an orchestral score combining the techniques of Herrmann and John Williams, and yet he only had twelve musicians other than himself to record with. He employed nine string and three brass players while he handled keyboards, altered piano, percussion, tin whistle, and vocal effects himself. The strings and brass, each spanning instruments from bass to treble, were overdubbed three times to make the final sound a little more voluminous. (The technique works well enough in this dry environment because it lends a sense of concentrated, intimate dread to the film.) The director sought a choral presence, too, so Manfredini generated slight, early synth choral effects used in cues like "Lights Out" and "I'm Mrs. Voorhees." The composer's altered "ki ki ki ma ma ma" vocals are the calling card for the music in the entire franchise, the "kill" and "mommy" abbreviations mimicking a famous line from the film. These echoing, whispered vocals are the de facto insanity motif in Friday the 13th, representing the bond between mother and son as they conduct their killing sprees. While synthetics do aid in the environment, the score mostly maintains an organic tone. Generally, the work is extremely prickly and unnerving, avoiding easy tonalities even in the finale that functions as false relief. Manfredini supplied three different broken chord sets as his foundation for the score, building from them a few recurring motifs but never allowing any of the ideas to express themselves very clearly. This is a score of atmospheric dread and piercing killing music, with neither pleasant and both extraordinarily grating. Film music enthusiasts will hear some of Herrmann's more challenging phrasing for violin rhythms, the fluid portions here taking inspiration from tense cues in Psycho and Vertigo. To an extent, these emulations, as well as similarities to Williams' Jaws, will distract.

While the psychotic "ki ki ki ma ma ma" vocals are the most obvious motif in the Friday the 13th scores, this first entry introduces a few other ideas that do recur. The most memorable melodic structure is a rising series of two and four-note phrases that sounds almost like the opening of the main theme from Williams' The Towering Inferno. It debuts in "Jeepers/Annie Gets It" but isn't fully developed until "Brenda in the Bathroom" and "Alice on the Couch." The idea opens "No Place to Hide" with slightly compelling dramatic weight and is often reduced to only the two opening notes in rhythmic form like Jaws, eventually trying to convey relief in the unused red herring of "Alice Walks Along the Lake." The flashier alternative in the score is Manfredini's killing motif, a metallic, high-pitched shrieking rhythm for violins. This slashing effect is used in "I'm Mrs. Voorhees" to make the killer connection, and it becomes frantic along with the main rising motif's fragments in "Jason in the Lake." The only other recurring melody comes from the theme of the "Sail Away Tiny Sparrow" country song heard as source early in the film; that melody returns in the contemporary rock of "Boat on the Water" with awful flanger distortion effects that make it sound literally underwater or, at the very least, like a slowed and warped tape. The combination cue, "Boat on the Water/Jason in the Lake," is the ultimate in jump scares, and while the light rock in the first half of this cue returns for the finale, Manfredini's intended "Final Shot" is a great, sequel-suggesting closing cue that went unused. In total, while the composer exceeded expectations in his creativity for Friday the 13th, the score set the stage from some of the genre's most obnoxious parody bait and remains largely unlistenable on album. Due to missing master tapes, the work was unreleased until 2012, when the La-La Land Records label extracted the music out of the film's mix as part of a set of the first six scores in the franchise. After it sold out, the label re-issued the same presentation of this score alone that same year. Years later, Paramount discovered the original recording tapes, but they were unmixed, which caused La-La Land to faithfully reconstruct the complete score and its various effects for what it called "The Ultimate Cut." This 2021 presentation doesn't always match what was heard in the film, but it essentially takes the original recording and works as much modern mixing magic into its final form, and the result is fascinatingly vibrant. This longer product also offers various cues without Manfredini's flanger effect, including an unmanipulated "Boat on the Water" version that is far superior. Concept purists will prefer the 2012 albums, but don't expect easy listening on either product.   @Amazon.com: CD or Download