The fourth Brandenburg Concerto is scored for violin, two flutes, strings, and continuo. Bach's score calls the flutes "fiauti d'echo", an unusual term which probably indicates that a recorder in F was intended. But does "d'echo" mean more than simply specifying which recorders were to be used? If indeed recorders, rather than the transverse flute, then one might presume that the softer sound of the recorder is intended as a sort of echo - except for the fact that the flutes appear from the start of the Fourth Brandenburg, even without the solo violin, and while they occasionally double the solo violin, they are rarely used in an echo function. They do occasionally "echo" each other, especially in the second movement, but one wonders whether Bach really thought of these repeated "echoes" as softer echoes, or merely as imitative passages, which we find so often in Baroque music.

The flutes in fact play a prominent role, which might make one think this concerto has a solo group (concertino), in the concerto grosso format, but the work is sometimes considered a solo concerto for violin, given the long passages for solo violin alone (without the flutes and with the orchestral strings providing limited support). Or perhaps the Fourth Brandenburg is an amalgamation of the two distinct types of concertos.

The Fourth Brandenburg Concerto is unique in that it is the only of the six in which all instruments are used in all movements. In the other concertos, the middle movements have a reduced instrumentation.