There are modern performing editions of four of Jarvis' psalm tunes on the Choral Public Domain Library (see
http://www.cpdl.org/wiki/index.php/Stephen_Jarvis).
Is there any evidence for an 1815-16 date for the publication of 'Twelve Psalm Tunes, and Eight Anthems'? The GB-Lbl copy is watermarked 1816 (as noted in the Hymn Tune Index - see
http://hymntune.library.uiuc.edu/menu.asp?KeyValue=JarvSTPT&SearchType=2&Choice=0), but this is only an earliest possible date for the publication - the review under 'New Music and the Drama' in the Monthly Magazine in November 1821 (as given on CPDL) seems to suggest that it was published rather later?
Regards,
Edmund.