Improvising chord-playing musicians who omit the root and fifth are given the option to play other notes. For example, if a seventh chord, such as G7, appears in a lead sheet or fake book, many chord-playing performers add the ninth, thirteenth or other notes to the chord, even though the lead sheet does not specify these additional notes. Jazz players can add these additional, upper notes because they can create an important part of the jazz sound. Lead sheets and fake books often do not detail how to voice the chord because a lead sheet or fake book is only intended to provide basic guide to the harmony. An experienced "comping" performer playing electric guitar or piano may add or remove notes as chosen according to the style and desired sound of that musician, but must do so in a way that still emphasizes the correct musical context for other musicians and listeners.