R. Kaiser could be:
Rudolf Kaiser (22/06/1876 - ?), a German composer; born in Nurnberg, Germany.
or:
Rudolf Kaiser (1867), a Musikschuldirektor and composer.
Missa de Requiem in G major, for choir and organ. It contains:
01. Requiem aeternam
02. Dies irae
03. Domine Jesu Christe
04. Sanctus
05. Benedictus
06. Sanctus
07. Libera me Domine