All just my personal opinion
Beethoven: 6 Variations on an Original Theme, WoO 77 — Ronald Brautigam (2010, fortepiano), Olli Mustonen (1995); Beethoven: Allegretto in B minor, WoO 61 — Ronald Brautigam (2010, fortepiano); Beethoven: 6 Ecossaises, WoO 83 — Alfred Brendel (1985)
Bach: 4 Duets, BWV 802-805 — Ton Koopman, Christophe Rousset; Bach: Chromatic Fantasy & Fugue, BWV 903 — Wanda Landowska (1933), Andreas Staier (1988), Christophe Rousset (1990), Ton Koopman (1986)
Ludwig Senfl (ca. 1486 – 1543): Songs and Instrumental Music — Wally Staempfli, Kurt Huber, Fritz Näf, Eugen M. Dombois, Ricercare-Ensemble für alte Musik Zürich, Michel Piguet; Tore Tom Denys, Patrick Denecker, La Caccia
Händel: Giulio Cesare in Egitto — Alan Curtis, Il Complesso Barocco, Marie-Nicole Lemieux, Karina Gauvin, Romina Basso, Milena Storti, Emöke Baráth, Gianluca Buratto, Filippo Mineccia, Johannes Weisser
Franz Schubert: Vocal Duets, Trios and Quartets — Ameling/Baker/Schreier/Laubenthal/Fischer-Dieskau/Gerald Moore; Hector Berlioz: Requiem (Grande messe des morts), op.5 — Ozawa/Boston Symphony Orchestra/Tanglewood Festival Chorus
Beethoven: Variations on the Minuet “à la Viganò”, WoO 68 — Mikhail Pletnev (1997), Olli Mustonen (1995), Ronald Brautigam (2011); Mendelssohn-Bartholdy: Organ Sonatas op.65 — Heinrich Gurtner (1989), Stefan Schättin (1995)