Even a casual glance at the score reveals an exceptionally rich and sophisticated orchestration unlike any that Mozart had previously employed, Apart from the "Turkish music", which will be dealt with later, it is the wind instruments in particular which are used in the most colourful combinations imaginable. Mozart specified four different types of clarinet: in C, in B flat, in A and basset horns, i,e. clarinets in F. The clarinets in C, in particular, which unfortunately are no longer used in classical music (with the exception of a few late romantic operatic solos) produce a timbre that is quite strange to present-day ears; their jaunty sound is only to be heard in folk music.
There is a pronounced tendency nowadays to unify different tonal colours and to play everything, wherever possible, on B flat clarinets. This has deprived the clarinet family of its variety with regard not only to tone colouring, but also to intonation. Mozart's clarinetists had to move very rapidly from one extreme to the other. For example, in aria No. 10 "Traurigkeit" they play basset horns, the lowest and most dark sounding type of clarinet, whereas aria No. 11, "Martern aller Arten", which immediately follows it, is played on clarinets in C, the brightestsounding member of the family. In this way Mozart achieves considerable contrasts by variation in tone colours.
Mozart's writing for the horns was also extremely differentiated. He specified horns in B flat, A, G, F, E flat, D and C - in a word, the complete scale of B flat. It is exciting for the listener as well as for the performer to discover that the composer did not indicate the register of the horns in B flat, so that in five numbers (Nos, 2, 6, 10, 15 and 20) one has to rely on the context to determine in which octave the horns were intended to play. (In Mozart's time the register of the horns in C and B flat was not abvious; they could be played "alto" without a crook at all or with a very short crook, or "basso" with a very long crook. As a rule the horns in C were played low, and the horns in B flat were played high, but there were many exceptions.) However, the register of the horns profoundly affects the sound pattern, indeed the harmonies, because the second horn, if played "basso", often drops below the bassoons. We have attempted to find a sensible rule that might enable the horn player to determine in which register he was supposed to play in places where the composer did not indicate "alto" or "basso", as is the case here. In No. 2 we decided for low horns because of the hint in bars 76-80, where Mozart requires a conversion to E flat horns: the first horn’s E flat would have been a very muffled stopped note on the low B flat instrument; in addition, an extreme and very risky change of register would be required. Bar 76 on low B flat horns; on high B flat horns; and on E flat horns, as written by Mozart.
With the exception of these bars the piece is therefore played in low register. No. 6 is low (otherwise there would be a large number of pedal notes); No. 10 is high (because of the combination with other wind instruments and the harmony - immediately obvious on account of the whole piece being in a somewhat lower register); No. 15 is low (because of the harmony and the register, but especially because of the horns' role in the wind ensemble of the allegretto passage in 3/4 time); No. 20 is high (here I felt that the interplay with the clarinets in B flat in bars 110ff, 135ff and 170ff and the epilogue demand the high register, as does the bright woodwind sound at "Wonne..." at bar 26 and analogous passages).
The "Turkish" instruments to which Mozart occasionally refers in the score as "Turkish Music" present a special problem. They are the big drum, called "tambura granda" and "tamburo turco", the "triangoli", the "piatti" or cymbals and the "flauto piccolo". To understand these instruments and their deployment one needs to study their provenance and role in the music of the time. It is a remarkable fact that until the invasion by the "Turkish music" there were no unpitched instruments in the classical orchestra at all. By contrast with, say, the timpani, "Turkish" instruments do not produce notes but noise with highly sophisticated colouring. Just as the Turks used "Janissary music" to inspire their own soldiers while terrifying the enemy’s, it was primarily adopted in the West for military purposes. When, during the course of the 18th century, the menace of Turkish invasion receded, the dangerous, spicy sounds and wicked, exotic colours became, as it were, succulent morsels to be savoured by connoisseurs. Many operas by Gluck and others are on that level.
But when Mozart and Haydn brought Turkish instruments into play in the "Entführung" and the "Military Symphony", entirely new elements of humanism and ethics were introduced. They were not interested in pleasurable thrills and fashionable novelties. The essence of percussion instruments is confrontation, indeed aggression: the drums are always being beaten for someone and against someone. The more they enhance the courage and fury of the one, the greater is the fear that they instil in the other. At the very first performance of the "Mi1itary Symphony" the public was quite horror-struck when the Turkish instruments suddenly instruded into the wonderfully peaceful andante. No doubt the audience at the first performance of "Entführung" experienced similar emotions when, after eight pleasurably exciting bars in C major, played piano, the relentless, brutal military arsenal of Turkish instruments burst forth. Directly and unexpectedly there follows the central section of the overture, in C minor, anticipating in its musical hopelessness the words of Belmonte’s opening arietta: Hier soll ich dich denn sehen (Is it here that I shall see you). The stress must lie on "hier" - in this place where brutality reigns, where people ar beaten. The central section is like a delicate plant that is crushed, shattered by the two blocks in C major. After the triangle's last threatening sounds have faded away, the central theme returns, this time in C major; now the stress is one the word "sehens"; it implies "to see again", and the music, too, expresses hope. - This overture, of which arietta No. 1 forms a part, lays down the ground rules, rather like a characterising chord, of the drama which follows. Just a brief explanation of the instruments: The flauto piccolo is not a Turkish instrument at all; evidently Mozart used it on account of its piercing sound and military associations. This piccolo flute was not a small transverse flute but a special member of the recorder family, a "flageolet" in G which, in spite of its extremely simple construction, has a wider range and shriller sound than even the modern piccolo. The tonal quality is piping, the loudness cannot be changed without affecting the pitch. - The triangle: On occasion Mozart wrote "triangoli", which suggests that he was calling for more than one instrument. Since, however, a single player cannot properly control several triangles, and experiments proved that rather than obtaining the required dynamic nuances their sound became obtrusive, we decided in favour of a single instrument. The piatti in the "Janissary music" were small, saucer-shaped instruments with broad rims rather like plates, cast in bronze, with a wide spectrum of sounds, in which a pitch can be discerned. It is particularly interesting to note (and, as far as I know, unique in classical music) that Mozart specified two different pitches: g” for the pieces in C major (the overture; chorus No. 5; No. 14; No. 21 from bar 120 onwards); and e” for the pieces in A minor (No. 3 from bar 14 onwards; No. 21 from bar 74 onwards). This clearly implies instruments tuned to different piches. It is also interesting that this is always the dominant rather than the tonic of the piece in question. On these cast cymbals, which Mozart also called "Cineln" (cinelli) the fourth is plainly audible; thus, in the case of the cymbals in g" one can clearly hear the c’ and in the case of the cymbals in e” the a’.
The tambura granda or tamburo turco is a tall drum with a relatively small diameter, carried across the body and beaten by the right hand with a heavy club-like drumstick, and by the left with a switch or birch. The sound produced by the club must be dry and muffled in order to contrast sufficiently with the timpani whenever they play at the same time. - It is not at all easy to achieve an entirely unpitched sound. - When this drum plays on its own one immediately is put in mind of someone being beaten or whipped. - The two types of drumbeat are normally indicated in the score by different note tails: J = whip, p = club. Remarkably, and strangely in the light of present-day appreciation of these percussion instruments, the first beats require the bright sound of the whip; this is evidently of considerably greater significance, quite apart from being more frightening, than the muffled thud. All the Turkish instruments were specially manufactured for this performance.
The two central arias of this opera, Konstanze's so-called "Marter" aria, No. 11, and Belmonte’s aria No, 17 "lch baue ganz auf deine Stärke" are structurally similar in that in each case the singer is counterposed to a group of instmmental soloists. This idea had already been put into practice by Mozart in "Idomeneo" in Ilia’s aria "Se il padre perdei" which deals with a similar subject, with a quartet of solo wind players. In Belmonte’s aria, a paean of praise to the power of love which can move mountains, the eight wind instruments (2 each of flutes, clarinets in B flat, bassoons and horns in E fiat) are also treated as soloists, as in a wind octet. In the absence of oboes the sound pattern becomes positively romantic, mostly on account of the mixture of clarinets and horns. - The layout of the "Martern" aria is really just as askin to chamber music. Although the tutti opening leads one to expect a grand bravoura aria in late baroque style, within a mere three bars the strings accompany a sensitive solo quartet consisting of flute, oboe, violin and cello. An exceptionally long introduction runs the gamut of all conceivable human emotions, the only missing element being the oft-mentioned cruelty. Selim loves Konstanze; it is obvious that a man of his high moral purpose could never be cruel, (In this article I can only refer to the results and not the considerations which have produced them.) The aria depicts the profound conflict of two lovers, the heart of the matter being Konstanze’s fear of succumbing to Selim's wooing (Nur dann würd' ich zittern: wenn ich unteu könnte sein - Only one thing could make me tremble: if I were to be unfaithful), because she already loves him. The "tortures" are presumably the lifelong sufferings of lovers who may not belong to one another, Konstanze having already plighted her troth to Belmonte. A striking feature of this aria is the often recurring sighing motif played by the four instrumental soloists; it is marked "ad libitum" and thereby taken out of the context of the tempo, the resumption of which is therefore naturally all the more effective.
This particularly striking modification of the tempo is just one of the many instances which indicate that the tempi and their adjustments were subject to the most meticulous calculation of their dramatic impact. There are other passages marked "ad libitum", "stringendo il tempo" and an unusual number of pauses. The frequent "tenuto" marking (sustaining the note without loss of volume) suggests that "non tenuto" singing was the norm. From the adagio C (No. 6 "Ach, ich liebte..."; No. 10 "Welcher Wechsel..."; No. 20 "Welch ein Geschick...") to the presto C of the overture there are in 21 numbers no less than 27 different tempo indications. The interrelation of tempi, musical figures and musical emotions is so compelling and indissoluble that there is hardly any scope for shaping the individual tempi, once certain basic speeds have been decided upon - possibly by reference to the acoustics in which the performance is to take place, the individual voices, the size of the cast; after that one tempo flows logically from another.