You may know that Constanze sang a soprano, but do you know on what degree she had her abilities? It is reported that she sang solo of Mass c minor K.427(417a) performed at Salzburg just before Mr. and Mrs. Mozart returned Vienna on October 26, 1783, and that she also sang role of Eugenia in the unfinished opera buffa "Lo sposo deluso" K.430(424a) two times by 1801.
And we may find a clue in several survived manuscripts of solfeggio and esercizi. From the notations "Per la mia cara consorte" on No. 1 and "Per la mia cara costanza" on No. 5 and the similarity of the beginning of No. 2 to that of the second part of "Christe eleison" in mass c minor K.427(417a) which Constanze sang, we surely assume that Mozart wrote these exercises for Constanze. I will try to read a characteristic of singing by Constanze from these exercises which are considered to have been written occasionally. (You can refer to each piece by MIDI file in which the soprano part is substituted by clarinet.)
Solfeggio in C major / E flat major (allegro, 4/4 time) (unfinished) K.393(385b)No.1
Autograph had been considered as lost but was reappeared in 1970's and now it is in possession of Villa Verdi, Sant'Agata (Parma). Though it was reported as16-staff upright-format (Hochformat) in the Köchel sixth edition by mistake, it is 12-staff oblong-format (Querformat) which is listed in Alan Tyson's watermark catalog as Vienna made paper. Because Mozart used this paper during 1781-87 years, we may admit the hypothesis that Mozart wrote this piece in 1782, particularly after the date of marriage, August 4, 1782.
The music is in 62 measures including 44 measures of C major (whole measures are repeated) and 18 measures of E flat major with unfinished ending. Unfinished shape is clear because full spaces are remaining. Because I can't think that Constanze sang the sequel impromptu, only a part of C major key would be used practically. A musical scale of wave shape with 8th notes and 16th notes make 2 measures, 4measures and 5 measures groups increasingly and are risen successively. As soon as it reaches the highest note 'b2' after the continuous rising musical scale with trills, it leaps down to notes 'b' and 'a'. Several confirmations of the highest tone 'b2' bring ending passing through D major and G major.
I refrain from comments on the part of E flat major because I cannot catch a unity from the facsimile, and I hope your suggestions about possible errors or miss understanding.(Facscimile is too small in the printing appearences.)
We may say that this piece is easier than other etudes as exercise concerning both height of voices and degree of difficulty.
Solfeggio in F major (adagio, 4/4 time) K.393(385b) No.2
Autograph is lost but only a facsimile exists and, perhaps, it is regarded as composition in 1782 because it is by 12-staff oblong-format paper possibly made in Vienna. As above mentioned the subject is same as what "Christe" in Kyrie (in E flat major, andante moderato) of Mass c minor K.427(417a). But two possible opinions will be proposed, i.e., (1) "Christe" is original and the etude quoted the subject to let Constanse be trained to be familiar on the subject, or (2) original etude is quoted to "Christe" to let Constanze feel daily household pace on the mass performance.
Which one has higher possibility? If this music was written aiming at the exercise of mass music c minor, the most difficult part in "Christe", i.e., the lowest note 'as' in whole note must come out. But the lowest note of this etude is 'b'. Rather, one of the highest note 'b2' is higher than 'a2' of "Chrisre". Accordingly, it is suggested that this music is an original etude and Mozart quoted the subject in mass music. In other word we can say that this music is sketch for Mass c minor, and it is recognized that Ulrich Konrad's catalog number "K.393(385b) Nr.2 zu K.427(417a)" is reasonable in Mozarts Schaffensweise (Göttingen 1992).
A tempo of adagio includes the principal objective of exercise of this music. As I set it in MM=46 here in MIDI file in accordance with Jean-Pierre Marty's The Tempo Indications of Mozart (London 1988), you may easily understand it requests high technique to sing this in tempo. Mozart once wrote about slow trills in his letter on October2, 1777: "The leading soprano is called Mlle Kaiser... When she sustains her voice for a few bars, I have been astonished at the beauty of her crescendo and decrescendo. She still takes her trills slowly and I am very glad. They will be all the truer and clearer when later on she wants to trill more rapidly, for it is always easier to do them quickly in any case" (quoted from Emily Anderson, editor, Letters of Mozart and his Family, London 1938; rev. 3/1985). We find many triplets in the latter half of music which may be more difficult to keep the tempo because triplets cause feeling of acceleration by itself. The music consists of 26 measures in all.
Solfeggio in C major (allegro, 4/4 time) K.393(385b) No.3
This music is written on the 10-staff-format paper made in Salzburg. Accordingly the composition date is assumed in the latter half of 1783 when Mr. and Mrs. Mozart stayed at Salzburg. An opposite hypothesis seems to give approval here other than what I described about Nr.2 above. Because it is supposed that not only composition was written during an exercise of the c minor mass but also the lowest note reaches 'as', we can assume that Constanze sang this etude for the objective of brushing up her technique for the coming mass performance.
As for what we can say more, music constitution of all 96 measures fills up in a musical scales and leaping patterns fully inclusively and we can also estimate this music surely fits in audience appreciation. Applause might be anticipated. Whose applause might it be? I think Mozart composed the music assuming that Leopold and Nannerl listen to the exercise of Constanze at the next door.
It is remarkable that the highest note is 'd3'. Of course her range of voice does not match Aloysia Weber's which was 'g1'-'g3 ' in K.316 but it is equal to the highest tone 'd3' for Constanze role of "Die Entführung aus dem Serail" by Caterina Cavalieri and to 'a'-'c3' for Fiordiligi role of "Così fan tutte" by Francesca Adriana Gabrielli (known as Ferrarese del Bene).
Esercizj K.393(385b) No.4
There are 7 pieces of music scales in 4 measures to 8 measures which may be used for voice warming up. They are written on 12-staff oblong-format paper made in Vienna which Mozart used from the first half of 1782 to 1784. It will be assumed that these are etudes for daily exercise for Constanze. The range of voice is from 'c1' to 'a2' which is narrower than all of other solfeggios.
Solfeggio in B flat major (andante, 2/4 time) K.393(385b) No.5
It is written on 12-staff oblong-format paper made in Vienna which Mozart used during 1781-1784. The music is decorative etude with many ornaments and is longest with all 133 measures. The range of voice is from 'b' to 'd3' where the highest tone is equal to that of Nr. 3 above. This music was also aimed to train the technique of Constanze.
As a summary of mentioned above, we say that Constanze was an excellent soprano singer in both a range of voice and a technique of singing. She received almost of all demand from Mozart and he surely accepted her talent.
Instruments; CH1: Soprano(Clarinetto), CH2: Basso(Fagotto)
Source; No.1: Facsimile in MJb1980-83 pp.430-431, No.2: NMA I/1/1/5 Anh.II, Nos.3-5: AMA