Many movements of Messiah exist in variant forms composed or adapted by Handel for his own performances. Reference is complicated by the fact that the three principal performing editions in use today number the movements differently. The system of references employed in the left-hand column of the libretto (Appendix 1, pp. 86–100) serves as a guide to the contents of these editions. The three editions are:

1. B Peters Edition, ed. Donald Burrows, vocal score 1987. This adapts the numbering system from the previous editions by Kurt Soldan (1939) and Soldan/Arnold Schering (1967).

2. S Novello Edition, ed. Watkins Shaw, vocal score 1959, and subsequent revised reprints. This adapts the numbering system from the previous edition by Ebenezer Prout (1902).

3. T Bärenreiter Edition, ed. John Tobin, vocal score 1972, derived from Tobin's full score in the Hallische Händel-Ausgabe (Serie I, Band 17, 1965). This edition provided the basis for the movement numbers in the thematic catalogue of Handel's works by Bernd Baselt in W. Eisen and M. Eisen (eds.), Händel-Handbuch Band 2, Thematisch-systematisches Verzeichnis (Leipzig, 1984), HWV 56 Messiah, pp. 178–97. Where Baselt's designations differ from or supplement T, the catalogue numbering is given under ‘Comments’ preceded by HHB.

B and S include many variant movements that are not in the preceding editions by Schering/Soldan and Prout, which explains why the numberings of the preceding editions required adaptation. Full scores of all three editions are in print from time to time.