Welcome all to the jazz mando workshop. The tune for this upload serves as a good introduction to the role of fourths in modern jazz. This is a complex sound and there are many applications in which it can be used, so for now we'll explore a brief overview of the subject.
The composition is McCoy Tyner's Blues on the Corner. McCoy Tyner is a powerful pianist with a thundering left hand and a predilection for '"fourthy" comping. He first became widely known when, while still in his early twenties, he joined John Coltrane's Quartet. He is still performing and recording extensively today and continues to create passionate music.
The use of stacked fourths creates an open, ambiguous sound by which one can cut through the diatonic underpinnings of a progression and introduce a more abstract and "free" feel. When soloing, arpeggiating in fourths can create its own logic, free from the usual considerations of which degree of the chord we are playing. Also, pentatonic scales (1,2,3,5,6) are used with these chords - for instance, a Bb pentatonic played with the Csus4, and so on. There's lots of room for experimenting here.
One of the elements I like in this tune (aside from the wonderful, swaggering street corner feel) is the fact that the progression starts off as a usual blues, then wigs out for a few measures, and returns to the familiar blues form. The solos are played over a straight jazz blues progression but the fourths can be referred to throughout.
The mandolin is well suited for playing fourths, they fall under the fingers easily. The sus4 chords I noted starting in the fourth measure are voiced (bottom to top) 5 - 1 - 4 , a Csus 4 would be played G - C - F. Of course you could call this chord by any number of other names, they are indeed slippery little devils. Good luck!
Will Patton