To help you secure the exact sheet music you need, please share a few more details: g., two-part, unison)?
A: Some editions offer the Sanctus a cappella . However, the original Missa Pro Europa includes an organ part intended to double the voices. If your PDF lacks it, use a piano to rehearse but omit it in performance for a pure sound. sanctus missa pro europa partition pdf
If you need help narrowing down your search or preparing this piece, please let me know: What is your choir? (SATB, SAB, or equal voices?) To help you secure the exact sheet music