<P> The exposition usually concludes when all voices have given a statement of the subject or answer . In some fugues, the exposition will end with a redundant entry, or an extra presentation of the theme . Furthermore, in some fugues the entry of one of the voices may be reserved until later, for example in the pedals of an organ fugue (see J.S. Bach's Fugue in C major for Organ, BWV 547). </P> <P> Further entries of the subject follow this initial exposition, either immediately (as for example in Fugue No. 1 in C major, BWV 846 of the Well - Tempered Clavier) or separated by episodes . Episodic material is always modulatory and is usually based upon some element heard in the exposition . Each episode has the primary function of transitioning for the next entry of the subject in a new key, and may also provide release from the strictness of form employed in the exposition, and middle - entries . André Gedalge states that the episode of the fugue is generally based on a series of imitations of the subject that have been fragmented . </P> <P> Further entries of the subject, or middle entries, occur throughout the fugue . They must state the subject or answer at least once in its entirety, and may also be heard in combination with the countersubject (s) from the exposition, new countersubjects, free counterpoint, or any of these in combination . It is uncommon for the subject to enter alone in a single voice in the middle - entries as in the exposition; rather, it is usually heard with at least one of the countersubjects and / or other free contrapuntal accompaniments . </P> <P> Middle - entries tend to occur at pitches other than the initial . As shown in the typical structure above, these are often closely - related keys such as the relative dominant and subdominant, although the key structure of fugues varies greatly . In the fugues of J.S. Bach, the first middle - entry occurs most often in the relative major or minor of the work's overall key, and is followed by an entry in the dominant of the relative major or minor when the fugue's subject requires a tonal answer . In the fugues of earlier composers (notably, Buxtehude and Pachelbel), middle entries in keys other than the tonic and dominant tend to be the exception, and non-modulation the norm . One of the famous examples of such non-modulating fugue occurs in Buxtehude's Praeludium (Fugue and Chaconne) in C, BuxWV 137 . </P>

Canon and fugue are the same musical forms