Arguments for and against including pieces with multiple attributions and/or challenged authenticity are presented in Clément Janequin: Life and Works: “Chapter 45: Conflicting attributions” and “Chapter 46: Challenged attributions.” Among the pieces discussed are:
“Nous bergiers et bergieres” no. 249 in ms. Copenhagen 1848.
(“Nous bergiers” is attributed to “Tomas Janequin” in the Copenhagen manuscript.)
“Joyeusement il fait bon vivre” fo. 32 in ms. Uppsala U87.
(“Joyeusement” appears without attribution in an Attaingnant print from 1530 in which another piece by Janequin is securely attributed to him.)
“Amour, amour” fo. 74 in ms. WhalleyS 23
(“Amour, amour” is clearly attributed to Janequin in the Whalley manuscript, but there is a strong possiblilty that this attribution was gleaned from the semi-corrupt Gardano 1541-13.)
“Mon pere m’a tant battu” fo. 17v in RISM 1558-19 (Fezandat)
(A version of “Mon pere” is attributed to Hesdin in RISM 1553-22 [LeRoy&Ballard], while the version in RISM by Fezandat with an attribution to Janequin is an instrumental arrangement.)
“Peine et travail” no. 16 in RISM 1552-10 (Susato).
The attribution to Janequin in the Susato print went unnoticed due to a library pasteover, and thus was excluded from Lesure and Merritt’s grouping of the 3-voice “arrangements” as LM220-230. As will have been noted, the present author is inclined to throw out all the three-voice selections in the LM editions, so the inclusion or exclusion of “Peine et travail” is academic, in all senses of the word.