Machikado-Mapoze's website for the album lists violin and viola in bullet points without performers, separate from everyone else. I'm not sure if this is because the players of those instruments are intentionally or unintentionally uncredited, or if they were actually played by Sakana Nakasako too and that section is just formatted confusingly. Nakasako has played violin before, on
Touhou Tatebue Eiyashou.