By comparing the added parts (which, to save space, are given only in compressed score) with the original bass, it will be seen that they are all founded on suggestions thrown out, so to speak, by Bach himself, on ideas indicated in the bass, and it is in obtaining unity of design by the scientific employment of Bach's own material that Franz shows himself so well fitted for his self-imposed labour. It has been already said that Bach requires more polyphonic treatment of the parts than Handel. The following extract from Franz's score of 'L'Allegro' ('Come, but keep thy wonted state') will show the different method in which he fills up a figured bass in Handel's music. The original stands thus—
which Franz completes in this manner—
Here it will be seen there is no attempt at imitative writing. Nothing is done beyond harmonising Handel's bass in four parts. The harmonies are given to clarinets and bassoons in order that the first entry of the strings, which takes place in the third bar, may produce the contrast of tone-colour designed by the composer.
6. It is quite impossible within the limits of such an article as the present to deal exhaustively with the subject in hand; enough has, it is hoped, been said to indicate in a general manner some of the various ways of filling up the orchestration from a figured bass. This however, though perhaps the most important, is by no means the only case in which additional accompaniments are required or introduced. It was mentioned above that the composition of the orchestra in the days of Bach and Handel was very different from that of our own time. This is more especially the case with Bach, who employs in his scores many instruments now altogether fallen into disuse. Such are the viola d'amore, the viola da gamba, the oboe d'amore, the oboe da caccia (which he sometimes calls the 'taille'), and several others. In adapting these works for performance, it is necessary to substitute for these obsolete instruments as far as possible their modern equivalents. Besides this, both Handel and Bach wrote for the trumpets passages which on the instruments at present employed in our orchestras are simply impossible. Bach frequently, and Handel occasionally, writes the trumpet parts up to C in alt, and both require from the players rapid passages in high notes, the execution of which, even where possible, is extremely uncertain. Thus, in probably the best-known piece of sacred music in the world, the Hallelujah chorus in the 'Messiah,' Handel has written D in alt for the first trumpet, while Bach in the 'Cum Sancto Spiritu' of his great Mass in B minor has even taken the instrument one note higher, the whole first trumpet part as it stands being absolutely unplayable. In such cases as these it becomes necessary to re-write the trumpet parts, giving the higher notes to some other instrument. This is what Franz has done in his editions of Bach's 'Magnificat' and 'Pfingsten-Cantate,' in which he has used two clarinets in C to reinforce and assist the trumpet parts. The key of both pieces being D, the clarinets in A would be those usually employed; the C clarinets are here used instead, because their tone, though less rich, is more piercing, and therefore approximates more closely to that of the high notes of the trumpet. One example from the opening chorus of the 'Magnificat' will show how the arrangement is effected. Bach's trumpet parts and their equivalents in Franz's score will alone be quoted.