Aleyn was an English composer. Two of his works survive in the Old Hall Manuscript

Old Hall Manuscript

The Old Hall Manuscript is the largest, most complete, and most significant source of English sacred music of the late 14th and early 15th centuries, and as such represents the best source for late Medieval English music. The manuscript somehow survived the Reformation, and until 1873 belonged to St...

, one a Gloria

Gloria in Excelsis Deo

"Gloria in excelsis Deo" is the title and beginning of a hymn known also as the Greater Doxology and the Angelic Hymn. The name is often abbreviated to Gloria in Excelsis or simply Gloria.It is an example of the psalmi idiotici "Gloria in excelsis Deo" (Latin for "Glory to God in the highest")...

 (no. 8), the other a Sarum Agnus Dei discant

Discant

Discant was a style of liturgical setting in the Middle Ages, associated with the development of the Notre Dame school of polyphony. It is a style of organum that includes a plainchant tenor part, with a "note against note" upper voice, moving in contrary motion...

 (no. 3, Old Hall, no. 128), later scratched out, which is ascribed to W. Aleyn. If this inscription is correct, the conflation of this composer and Johannes Alanus

Johannes Alanus

Johannes Alanus was an English composer. He wrote the motet Sub arturo plebs/Fons citharizancium/In omnem terram. Also attributed to him are the songs "Min frow, min frow" and "Min herze wil all zit frowen pflegen", both lieds, and "S'en vos por moy pitié ne truis", a virelai...

, who wrote Sub Arturo Plebs, is incorrect. David Fallows ascribed this Agnus to W. Typp, however it seems that he was mistaken.