II-01-01-Puer Natus – Introit for Christmas

Isaac’s mastery of cantus firmus polyphony is on full display as he sets the traditional opening chant for Christmas. The chant is echoed in all voices but is carried throughout in the tenor even though the incipit is in the soprano. Rhythmically, this is not a terribly challenging motet, but its charm comes in its beautiful phrases and harmonies. Based on Psalm 98, the lyrics reference God’s oversight of the Earth.

Puer natus est nobis et filius datus nobis
Cujus imperium super humerum ejus et vocabitur nomen ejus, magni consili Angelus
Cantate Domino canticum novum quia mirabilia fecit

Unto us a child is born and to us a son is given. Dominion is on His shoulder and His name shall be called the Angel of Great Counsel. Sing unto the Lord a new song for He has done marvelous things

Viderunt omnes fines terrae salutare Dei nostre.

All the ends of the earth have seen the salvation of our God.

II-01-02-Dies Sanctificatus – Alleluia for Christmas

Interesting textual settings abound in this motet. The Formschneider print is quite careless with the text, something that one might think would not be the case in music for such an important feast day. Words are omitted or the chant melody is ignored in several cases. As always, anything in brackets has been added by the editor and was not in the original print. Other oddities are noted in the score. Isaac’s use of word painting is on display throughout (“descendit”, “lux”, etc.). The melody is usually in the uppermost voice – even when the soprano part is silent. The SA parts are often in duet as are the TB voices.

Alleluia. Dies sanctificatus illuxit nobis:
Venite gentes, et adorate Dominum.
Quia hodie descendit lux magna super terra. Alleluia.

Alleluia. A holy day dawns on us
Come ye people and worship the Lord
for today a great light has descended to earth. Alleluia.

II-01-03 – Natus Ante Saecula – Sequence for Christmas Day

By 850 C.E., most chants for the Christian liturgy were codified thanks to the efforts of (first) Pope Gregory (540-604) and then the Holy Roman Emperor Charlemagne (748-814), who used Christian liturgy to unify his far-flung empire. Following that, creativity shifted to the elaboration of liturgical chant. New texts (tropes) were inserted into the melismas of existing chants, and both texts and melodies (sequences) were created to enhance the Proper of the Mass. Notker Balbulus (c.840-912), a monk at the great monastery of Reichenau near Constance (the Abbot of Reichenau and the Prince-Bishop of Constance were often the same person) is credited with the creation of many sequences; among them this sequence for Christmas Day.

Hans Buchner was the organist for Constance during Isaac’s stay there. He was also the pupil of Paul Hofhaimer, organist for the Maximilian’s Hofkapelle. Buchner’s Fundamentbuch records his organ settings for the verses of this sequence not set by Isaac. The fact that Buchner recorded the verses NOT set by Isaac are indicative that Mahrt’s theory of organ improvisation for the verses not set by Isaac’s polyphony is probably what was intended. In this instance, Isaac sets the “b” portions of the six verses while Buchner sets the “a” portions. Buchner’s music can be found in Erbe deutscher Musik, Bands 54-55 (Frankfurt: H. Litolff’s Verlag, 1974) edited by Jost Hanno Schmidt.

Neither Isaac’s nor Buchner’s melodies match what is recorded by Richard L. Crocker in The Early Medieval Sequence (University of California Press, 1977) or Lance Brunner in Early Medieval Chants from Nonantola (A-R Editions, 1999) for this sequence. For instance, the Buchner opening does not quote the beginning of the original Notker melody but rather, it uses the “b” section of the chant for its improvisation. Meanwhile, Isaac’s setting of the “b” section of the first verse uses the chant of that section, but it also quotes the “a” section of Notker’s original melody in the second phrase. Because sequences originated as tropes – poems attached to melismatic chant alleluias – the similarities between the alleluia Dies Sanctificatus for Christmas Day and the melodies in both Isaac’s and Buchner’s polyphony are significant. Other interesting interplay occurs such as the Buchner opening of the seventh verse being quoted in the Isaac polyphonic response. There are places in the Isaac motet such as mm. 52-56 where a voice part appears to be a chant quotation (the soprano voice in this iinstance) but I cannot identify a corresponding chant line.

Other mysteries present themselves such as, a) neither Buchner’s nor Isaac’s setting of verse 5 have any resemblance to the traditional sequence melody, although they both open in triple meter; b) both Isaac and Buchner set the last couplet (6B), something that might discredit the whole theory of their connectivity; c) both musicians seem to have been using the opening melody of the third verse as a motto for many of the verses – which is another connection to the opening of the Dies Sanctificatus chant; and d) there are textual differences between what is recorded by Crocker and Brunner and the Formschneider prints.

Editorially, this motet presents all sorts of challenges. One of the more interesting occurs in verse 4 where the bass part is notated in a series of changing mensural signatures and proportional changes. The bass part in the Formschneider print looks like this:

while the Soprano, alto, and tenor parts are notated in ¢. O is triple meter but at a higher tactus level than ¢, meaning that a breve here transcribes as a whole note rather than a half note. So, the first mensura (our modern day “measure” ought to be notated in 6/2 meter, equivalent to three measures of ¢. Similarly, a measure of C would be twice as long as a measure of ¢.  The longa following the C section is in ¢ and so, like the other three voices is transcribed as a whole note. Immediately following that is a 2:1 proportion sign, followed a little later by a 4:1 proportion sign. After working out all the other parts, it becomes obvious that the 4:1 proportion following the 2:1 proportion cannot be cumulative, but instead refers back to ¢ which is the common mensural signature of the time. After working all this out, the bass voice becomes this:

The puzzle about this notation is why Isaac would go to all that trouble to confuse the bass singers. My (unproven) theory is that he purposely used this notation as a joke or challenge. He knew these singers personally having worked with them for a least two years during the Reichstag in Constance. There is no other logical reason why he would have used such an arcane musical notation. Of course, the possibility exists that Isaac never used this notation and that in the intervening years between Constance and Nuremberg, the notation was changed.

From a performance standpoint, one could sing the non-Isaac sections as chant either with a soloist or in unison. However, the Buchner settings from the Fundamentbuch or something similar is probably what was used and given a competent organist and venue, are preferred. In the original performance the alleluia Dies Sanctificatus would have been sung up to the end of the alleluia verse. Then the sequence would have been sung, followed by the alleluia chorus.

1. Natus ante saecula Dei filius invisibilis, interminus, Per quem fit machina caeli ac terrae, maris et in his degentium, 

 2.Per quem Dies e horae labant et se iterum reciprocant, Quem angei in arce poli voce consona semper canunt: 

3.Hoc corpus assumpserat fragile Sine labe originalis criminis de carne Mariae virginis quo primiparentis culpam Aevaeque lasciviam tergeret. Hoc praesens die cula loquitur Praelucida, adaucta longitudine, quod sol post radio sui luminis vetustas mundi depulerit genitus tenebras

4.Nec nox vacat novi Sideris luce, quod magorum oculos terruit scios: Nec gregum magistris defuit lumen, quos praestrinxit claritas militum Dei.

 5.Gaude, Dei genitrix, quam circumstant obstetricum vice concinentes angeli gloriam Deo. Christe patris unice, qui humanum nostril causa forman assumpsisti, refove supplices tuos,

6.Et quorum participem te fore dignatus es, Jesu, degnanter eorum suscipe preces, Ut ipsos divinitatis tuae participes Deus, facere digneris, unice Dei.


1.Born before the beginning of time, the Son of God, beyond perception or limit, Through whom the workings of heaven and earth were made, of the sea, and all things therein,

2.Through whom the days and hours flicker and rekindle, Whom the angels in heaven continually proclaim with harmonious voice:

3.He took on a fragile body – without stain of original sin from the flesh of the Virgin Mary – through which the guilt of the first parent and the lust of Eve were wiped clean. Therefore, the present short day, sun past the radius, of brilliant light, speaks forth because the newly begotten Son, by the rays of its light, has expelled the long-standing darkness.

4.The night did not lack the light of the new star, for it struck fear in the knowing eyes of the Magi. Neither was the light invisible to the shepherds, for they were awestruck by the glory of the heavenly hosts.

5.Rejoice, O Mother of God, whom, in place of a midwife are surrounded by angels singing “Glory to God”. O Christ, Only Begotten, you who have taken human form for our sake, restore your humble servants;

6.And you humbled yourself that you might share in their suffering:, Jesus, deign to receive their prayers, So that you might make them participants of your divinity, O only God!

II-01-04 – Viderunt omnes – Communion for Christmas Day

This motet is an excellent example of free polyphony with only a passing nod to the original chant. While the incipit and first three notes of the soprano voice echo the chant from the Liber Usualis, no chant sources reflect the melodic phrases in this short motet. As was common in the pre-Tridentine liturgy, communion music is not lengthy even for this, one of the holiest of days, because the elements were only consumed by the small group of officiating clerics. Most attendees were observants.

Viderunt omnes fines terrae Salutare Dei nostre.

All the ends of the earth have seen the salvation of our God.

II-03-02-Vidimus Stellam – Alleluia for Epiphany

The alleluia response is notated in ¢3, which has semibreve equivalency with ¢ – the meter for the verse. The dotted half note of the alleluia should be the same as the half note of the verse. As often occurs in ¢3 meter, a hemiola imbedded in the tenor and bass voices in the first and second measures and again as the tenor approaches the cadence at the end of the alleluia. Metrical emphasis should be placed accordingly. Isaac’s textual mastery is on display in the verse as imitative polyphonic duets predominate until the words “adorare Domini”.

Alleluia. Vidimus stellam ejus in Oriente, et venimus cum muneribus adorare Dominum. Alleluia.

Alleluia. We have seen his star in the East and come with gifts to adore the Lord. Alleluia.

II-04-04-Responsum Simeon – Communion for the Feast of the Presentation (Candlemas) 

Also known as the Feast of the Presentation or Candlemas, in former times this feast on February 2 marked the end of the Christmas season (not Epiphany as is often thought). No individual voice seems to own the chant melody in this motet, and, after the opening phrase, the chant seems to be freely paraphrased throughout and difficult to identify. Nonetheless, it is a charming shorter piece with a very modal harmonic bent, perhaps meant to portray the age of Simeon.

Responsum accepit Simeon a Spiritu Sancto non visurum se mortem nisi videret Christum Domini.

Simeon had received a revelation from the Holy Spirit that he would not see death before he had seen the Lord’s Messiah.

II-05-03-Ave Maria – Tract for Annunciation

This lengthy six-movement motet is simply a joy to perform. It opens with a duet in the tenor and bass voices, which may be performed as a true duet or with all the men. In the second section, the alto voice joins the tenor and bass for a trio. The third section begins with a short opening by the alto and soprano voices who are then joined by the tenor and bass. Some antiphonal homophony at “et paries filium” (and bear a son). The fourth section, Mary’s response to Gabriel, is a duet for the soprano/alto voices. The full choir returns in the fifth section with Gabriel’s answer “The Holy Spirit shall come upon you…” Isaac reserved some of his best and intricate writing for the final movement. It opens with an alto/tenor duet and joined by the bass just to enter a section of blackened notes (triple meter) leads into the soprano voice soaring in at the words “Son of God”.

Ave Maria gratia plena Dominus tecum.
Benedicta tu in mulieribus et benedictus fructus ventris tui.
Ecce concipies et paries filium et vocabitur nomen ejus Emmanuel.
Quomodo inquit fiet quoniam virum non cognosco et respondens angelus dixit intrabit:


Spiritus sanctus superveniet in te et virtus altissimi obumbrabit tibi.

Ideoque quod nascetur ex te sanctum vocabitur Filius Dei.

Hail Mary, full of grace. The Lord is with you.
Blessed are you among women and blessed is the fruit of your womb.
Behold, you shall conceive and bear a son, and His name shall be called Emmanuel.
How shall this be, since I know not any man? And the angel answered and said unto her:
The Holy Spirit shall come upon you and the power of the Most High shall overshadow you.

Therefore, that Holy One which shall be born of you shall be called the Son of God.

II-06-01-Resurrexi – Introit for Easter

In a wonderfully inventive motet, Isaac uses the Easter introit chant as the basis for his polyphony while simultaneously troping the Latin version of the German hymntune Christ ist Erstanden (Christus surrexit). I have italicized the trope text in the score to make it more clear to the singers. The trope is in brackets below.

Resurrexi et ad huc tecum sum, alleluia.

[Christus surrexit mala nostra texit]

posuisti super me manum tuam, alleluia.

[et quos hic dilexit hos ad coelos vexit]

mirabilis facta est scientia tua, alleluia, alleluia.

Domine probasti me et cognovisti me.

Tu cognovisti sessionem meam et resurrectionem meam

I am risen and am always with you. Alleluia

[Christ is risen. He has covered our evil works.]

You have placed your hand upon me, alleluia.

[and those whom he loves he will lead to heaven]

Your wisdom is shown to be most wonderful, alleluia, alleluia.

Lord, you have searched me and known me.

You know when I sit down and when I rise up

II-06-02-Haec Dies – Gradual for Easter

This motet has one of the most challenging textual underlays to set. The chant source is the Graduale Pataviense. It can therefore be surmised that either 1) this motet was composed for the Imperial Hofkapelle, 2) the Konstanz diocese used the same chant, or 3) the Konstanz diocese used the same chant but the motet was part of the Constance commission. Regardless, there are many questionable text placements in the Formschneider print. I have documented the places where I have varied greatly from the source.

Haec dies quam fecit Dominus. Exsultemus et laetemur in ea.

This is the day that the Lord has made. Let us rejoice and be glad in it.

II-06-03-Pascha nostrum – Alleluia for Easter

Just as its companion motet above, this motet’s textual underlay is a minefield of guessing games. The chant source is the traditional alleluia for Easter Sunday, easily found in the Liber Usualis, Graduale, Romanum, Graduale Pataviense, etc.. I have documented those places where variances from the Formschneider were made. Some of these phrases are incredibly long requiring either instrumental doubling or multiple voices for covering individual breaths.

Alleluia. Pascha nostrum immolatus est Christus. Alleluia.


Alleluia. Christ, our Passover, is sacrificed for us. Alleluia.


II-07-01-Viri Galilei – Introit for Ascension

A bright, triumphant fanfare for a festal day. The chant is easily identified. The meter changes from ¢ to ¢3 at the initial alleluia with the tenor and bass voices in blackened notes (a device in the CC always signifying a hemiola when in triple meter). Those voices are therefore notated in duple rather than triple meter at that spot.

Viri Galilaei, quid admiramini aspicientes in caelum? alleluia:

quem admodum vidistis eum ascendentem in caelum, ita veniet, alleluia, alleluia, alleluia.

Omnes gentes plaudite manibus: Jubilate Deo in voce exsultationis

Men of Galilee, why are you gazing in astonishment at the heavens? Alleluia.

Just as you have seen Him ascend into heaven, so, in like manner shall He return. Alleluia, alleluia, alleluia.

All people, clap your hands, shout unto God with a voice of exultation.

II-08-02-Veni Sancti Spiritus – Alleluia for Pentecost

Isaac displays his genius for cantus firmus writing in using two chants as the basis for this motet. The plainsong alleluia for the corresponding mass (Liber Usualis, 1952, p.880) as well as the following more familiar sequence Veni sancte Spiritus are both evident in this polyphony – the alleluia chant in the alleluia verse and the sequence chant quoted by the soprano in the alleluia refrain – albeit with an altered semifinal tone. The Formschneider print has a printing error in that the soprano part shows C3 at the beginning of the verse. Pätzig (1956) shows two manuscript sources with the soprano in ¢3 as the bass voice is. This motet clearly shows the transition happening throughout the Renaissance as modality began its transition to tonality. The harmony has several different interpretations, again thanks to the variants between the print and the manuscripts.

Alleluia. Veni sancte Spiritus reple tuorum corda fidelium et tui amoris in eis ignem accende. Alleluia.

Alleluia. Come Holy Spirit into the hearts of Your faithful, and kindle in them the fire of Your love. Alleluia.

II-13-02-Magnificat – Alleluia for the Visitation

This lovely motet is a setting of two Magnificat chants. The first chant, Tone 5 (Liber Usualis, 1952, p. 210), is quoted in the soprano voice at the beginning of the alleluia and again at the beginning of the verse. The second chant, Tone 8 (Liber Usualis, 1952, p.212), is quoted or paraphrased extensively in all voices throughout. The text underlay in the Formschneider print is capricious, perhaps because the chants would have been so familiar to the singers. Editorial decisions have been indicated. The alto and tenor parts have nearly identical ranges so care must be taken to ensure homogeneity between those voices. The harmonic fabric is quite advanced, with the use of accidentals in the score to move the piece from a tonal center of F to B-flat and back.

Alleluia. Magnificat anima mea Dominum:

Et exsultavit spiritus meus in Deo salutari meo. Alleluia.

Alleluia. My soul magnifies the Lord.

And my spirit exults in God, who saves me. Alleluia.

II-24-01-Sacerdotes – Introit for the Feast of St. Conrad

Conrad is one of the patron saints of Konstanz and so this Proper was undoubtedly one of those created for the cathedral. This introit begins with the bass voice in ¢2 with the other voices notated in ¢. It makes for an interesting transcription puzzle and indicates that the chant resides in the bass voice. In similar fashion, the verse bass voice is notated in ¡ with the others in ¢ until the last seven notes of the bass voice join the rest of the voices in ¢. The chant is similar to that in the modern Gradual Romanum, but the Graduale Pataviense version is closer to that used here.

Sacerdotes tui Domine induant justiciam et sancti tui exsultent propter David servum tuum, non avertas faciem Christi tui. Memento Domine David. Et omnis mansuetudinis ejus.

Domine probasti me et cognouisti me.


May your priests, Lord, put on righteousness and holiness in imitation of David your servant. Do not turn the face of your Christ away. Lord, remember David and all his troubles.

The Lord has proved me and known me.

II-24-02-Ecce Sacerdos- Alleluia for the Feast of St. Conrad

This beautiful motet was transcribed and edited for Wilm Geismann when he was the director of music at the Konstanz Munster. It was subsequently published by Randall M. Egan, Publisher of Music, Ltd. in 2002 and is still in print and available from that publisher.

Alleluia. Behold a great priest who in his day pleased God and was found to be just, holy Conrad. Alleluia.

II-24-04 – Beatus Servus – Communion for the Feast of St. Conrad

Portions of the tenor voice and soprano voice have striking similarities to the communion Beatus servus chants found in the Graduale Pataviense and Gradual Romanum. I have indicated the quilisma found in those chants in the incipit and tried to indicate those notes which appear to match what chant sources I can identify. The chant specific to Conrad in the Constance diocese might have been like these other chants for the saints but have variances for this local saint.

Beatus servus quem cum venerit Dominus invenerit vigilantem amen dico vobis super omnia bona sua constituet eum

Blessed is the servant whom the Lord, when He comes, will find vigilant. Truly, I say to you, He will establish him over all His possessions