'As for singing upon a plainsong, it has been in times past in England, as every man knows, and is at this day in other places, the greatest part of the usual music which in any church is sung, which indeed causes me to marvel how men acquainted with music can delight to hear such confusion as of force must be among so many singing extempore [such as Adriano Banchieri: see the notes below]. But some have stood in an opinion which seems not very likely to me, that is, that men accustomed to descanting will sing together upon a plainsong, without singing either false chords or forbidden descant with each other, which until I see it I will ever think to be impossible. For although they might all be the most excellent men, and every one of their lessons [parts] very good individually against the cantus firmus, even then is it impossible for them to be true to one another...'
'As for singing vppon a plainsong, it hath byn in times past in England (as euery man knoweth) and is at this day in other places, the greatest part of the vsuall musicke which in any churches is sung. Which indeed causeth me to maruel how men acquainted with musicke, can delight to heare such confusion as of force must bee amongste so many singing extempore. But some haue stood in an opinion which to me seemeth not very probable, that is, that men accustomed to descanting will sing together vpon a plainsong, without singing eyther false chords or forbidden descant one to another, which til I see I will euer think vnpossible. For though they should all be moste excellent men, and euery one of their lessons by it selfe neuer so well framed for the ground, yet is it vnpossible for them to be true one to another...'
Thomas Morley, A Plain and Easy Introduction to Practical Music (London: Peter Short, 1597). My paraphrase for ease of understanding.
Adriano Banchieri, Cartella Musicale Nel Canto Figurato, Fermo, & Contrapunto (Venice: Giacomo Vincenti, 1614), p.230. My Translation.
London, British Library, Add. Ms. 4911 [GB-Lbl Add. 4911]. Available online at <http://www.bl.uk/manuscripts/FullDisplay.aspx?index=0&ref=Add_MS_4911>
It's worth comparing this passage with a contrasting perspective on the same phenomenon described by Adriano Banchieri almost twenty years later:
'In Rome...while singing [extempore] counterpoint, in the mind (alla mente) above the bass, nobody does that which his partner sings, but everyone, with certain observations conferred among them, creates a very delightful [gustosissimo] sound, and this is a general custom, let a hundred different voices sing (as it were) consonantly above the bass, everything in accordance, and those few bad fifths and octaves, strangenesses [stravaganze] and dissonances [urtoni] are all the graces which make the true effect of improvised [alla mente] counterpoint...’
‘In Roma...mentre cantano il Contrapunto, alla mente sopra il Basso, niuno fa quello che cantar deve il compagno, ma tutti, con certe osservazioni tra di loro conferite rendono un udito gustosissimo, & è questa una Massima generale, cantino pure cento variate voci (per così dire) consonantemente sopra il Basso tutte accordano, & quelle cattive più Quinte ottave, stravaganze & urtoni sono tutte gratie che rendono il vero effetto del Contrapunto alla mente...’
Below is an example from the anonymous Scottish 'Art of Music', GB-Lbl Add. 4911, penned c.1580, accompanied by the comment that this example includes 'tua sightis of discant upon the plane sang...with formal concordance' ('two sights of descant upon the plainsong in proper consonance.')
Although individually each of these upper voices demonstrate the same contrapuntal language as the two-voiced examples from earlier in the chapter (including the spicy dissonant accented appoggiaturas), a number of the 'false chords' and examples of 'forbidden descant' described by Morley occur between the two. Of particular interest are the letters which appear at the same point in all parts, presumably in an effort to coordinate the reader of the example when reading all three parts together in the manner of rehearsal marks in a modern score.
The most notable contrapuntal irregularities between the two upper voices are as follows:
1. The first beat of bar eleven, the 4-3 suspension above the chant is present in both voices, and resolves in unison to the note below, albeit with decoration in the upper voice.
2. In the second crotchet of bar fifteen, the two upper voices move in parallel fifths.
3. In the second minim of bar seventeen, the upper voice enters on an A as the lower voice sings a G whilst running downwards.