There is a pitch, to be sure, but its musical value is more rhythmic than melodic or harmonic...they add momentum and drive to any bass line.
The unaccented notes in such a pattern as a clave are considered to represent the mean level of emphasis—they are neither absolutely emphasized nor unemphasized.
This can be a very fine distinction, and the ability of an instrumentalist to differentiate between what is a ghost note and what is a rest is governed largely by the acoustic nature of the instrument.
[6] According to The Drummer's Bible: How to Play Every Drum Style from Afro-Cuban to Zydeco, the purpose of a ghost note is to "...be heard under the main sound of the groove.
Percussion music in particular makes use of anti-accent marks, as follows: [citation needed] Examples can be heard in the drumming of Harvey Mason, Mike Clark, Bernard Purdie,[7] Brad Wilk, David Garibaldi, Karen Carpenter, and Chad Smith.
[8] Particularly recognizable examples of this technique are Gregory C. Coleman's drum break in "Amen, Brother" by The Winstons, Clyde Stubblefield's beat in "Cold Sweat" by James Brown[9] and Jeff Porcaro playing the beat for the Toto hit "Rosanna".
With the double bass, slap-style ghost notes are used in rockabilly, bluegrass, and traditional blues and swing jazz.
As an extreme example, the opening number of The Music Man, "Rock Island", is written almost exclusively in ghost notes.