the 'Königliche Musik-Institut,' choir-master at the Catholic church of St. Hedwig in Berlin (1846), member of the 'Akademie der Künste,' and joint-founder with Theodor Kullak of the Berlin 'Ton-Künstler-Verein.' He is best known as the editor of the following important works:—'Collectio operum musicorum Batavorum saeculi XVI,' 12 vols.; 'Musica sacra XVI, XVII, saeculorum,' 13 vols., containing organ-pieces, masses and motets for men's voices and full choir; 'Collection de compositions pour l'orgue des XVI, XVII, XVIII siecles,' 6 parts. 'Cantica sacra … aus den XVI–XVIII Jahrh." 2 vols. Commer has also composed some church music, Lieder and dances for pianoforte. [App. p.595 adds "date of death, Aug. 17, 1887, and that 14 vols. of 'Musica Sacra' have now appeared, of which only the earlier volumes were edited by Commer."]
[ A. M. ]
COMMON TIME. The rhythm of two or four beats in a bar, also called Equal time. According to the method of teaching usually observed in England, common time is divided into two kinds, Simple and Compound, Simple common time including all rhythms of two or four in a bar, except those in which the 'measure note,' or equivalent of a beat, is dotted; while a rhythm of two or four beats, each of which is dotted and therefore divisible into three, is called Compound common time. Thus 4-4 time or four crochets in a bar, and 2-4 or two crochets, are simple common times; while 6-4 or six crochets, 6-8 or six quavers, and 12-8 or twelve quavers, are compound common, because though the number of beats in a bar is even, each beat is of the value of three crochets or quavers respectively, and may be expressed by a dotted note. A better and more logical method is that taught in Germany, by which all rhythms are divided into Equal and Unequal, that is having two or three beats as a foundation, and each of these again into Simple and Compound; simple rhythms being such as have either two or three beats in a bar, the first alone accented, and compound rhythms those in which each bar is made up of two or more bars of simple time, and which have therefore two or more accents, the first being the strongest. It will be seen that according to this system, 4-4 time, which we call simple common time, will be considered as compound common, being made up of two bars of 2-4 time, just as 6-8 is compound common, being made up of two bars of 3-8 time. And this plan has the advantage that it allows for the secondary accent which properly belongs to the third beat of a bar of 4-4 time, but which is not accounted for by the theory that the time is simple.
Although the term common time is generally applied to all equal rhythms, it properly belongs only to that of four crochets in a bar, the tempo ordinario of the Italians, denoted by the sign 
, which is a modernized form of the semicircle 
of the ancient 'measured music,' in which it signified the so-called 'tempus imperfectum' or division of a breve into two semibreves, in contradistinction to 'tempus perfectum' in which the breve was worth three. Another relic of the ancient time-signatures which is of importance in modern music is the sign of the 'diminutio simplex,' which was a semicircle crossed by a vertical line 
, and indicated a double rate of speed, breves being sung as semibreves, semibreves as minims, and so on. The modern form of this sign, 
, has much the same signification, and indicates the time called 'alla breve,' or two minima in a bar in quick tempo. [See Breve.]
[ F. T. ]
COMMUNION SERVICE. The ancient counterpart of the English Communion Service, the Mass, has always been looked upon by those who have held music to be an important part of worship as a fit opportunity for displaying the grandest resources of musical effect. The magnificent works which have been produced by great masters for the use of the Roman church are well known to musicians, but for a variety of reasons which this is not the place to discuss, the English Communion Service has not been so fortunate, though the words available for musical purposes are almost the same. Most of those remarkable composers who wrote the music for the English services in the early days of the Reformation have been far less liberal of their attention to this than to the ordinary Morning and Evening Services, having been content to write music merely for the Creed and the Kyrie, and sometimes the Sanctus. This was evidently not the intention of the compilers of the service, nor was it the idea of Marbeck, who adapted the first music for it. In the first Prayer Book of Edward VI the Communion Service was ordered to be introduced by an 'Introit,' according to an ancient custom of the Western church, which was sung to a chant. This injunction was omitted in later editions, but the custom of singing while the priest goes up to the altar still continues, though there is no rubrical direction for it. At one time it became customary to sing a Sanctus, but that seems to be growing into disfavour at the present time.
The Offertory sentences were ordered to be said or sung, and for them also there is music in Marbeck, but none in later composers of the early period, probably because the word 'sung' was afterwards struck out of the rubric, and the sentences ordered to be read by the priest—an order which does not now prevent their being sung by the choir in many churches after the manner of an anthem. The Kyrie which follows each commandment is almost universally sung wherever there is any music in the service at all, and the settings of it are fairly innumerable. Many attempts have been made to vary the monotony of the repetitions by setting each to different music, by varying the harmonies of a common melody, or by alternating harmony and unison of the voices. The latter probably best hits the desired mean between musical effect and comprehendibility.
The Creed has invited most composers who have written for the service at all. Marbeck's setting of it with the 'Gloria in excelsia' is the freest and most musical of all his arrangement. [Creed.] With the Creed most frequently ends the musical part of the service, probably because there has been a very general prejudice against unconfirmed choir-boys being present at the celebration. Hence also there is not much
