Jimi Hendrix was often characterised by his exotic appearance and extravagant performance, but underneath these trappings was an extraordinary guitarist who managed to transform some of the key elements of blues and rhythm-and-blues traditions. An important feature of Hendrix’s music is his characteristic use of the seventh chord with a sharp ninth, or the augmented ninth chord, now often referred to as the ‘Hendrix chord’. This paper examines some ways in which Hendrix used this chord by surveying and drawing comparisons between various instances. It is not necessarily the fully voiced version of the chord that Hendrix used, but interval combinations drawn from or related to it, with particular timbres and articulations. Together these define what might be called a ‘sharp ninth sound’. Through register placement, timbre, articulation, and chordal function, it is intimately tied to the blues idiom, adding a blues tonal element. This is one aspect of Hendrix’s music, then, that shows his deep roots in the blues.