The Golden Piano in Deltarune Chapter 4 is in the Dark Sanctuary, above the Old Man’s study/library area. From the study, go to the top-left doorway, then climb the bookshelf paths on the right to reach it.

Route

  • Start in the Old Man’s study.
  • Go through the top-left door into the library area.
  • Head to the right-side climbable bookshelf.
  • Climb up again at the next section to reach the Golden Piano.

Notes

  • You need the three music-note clues before the piano puzzle is useful.
  • Several guides describe the same general path, with small route variations depending on how you enter the library area.

Puzzle input

The input commonly listed for the Golden Piano is: Up, Dot, Up, Left, Down, Dot, Right, Dot, Right, Down, Left, Dot.

TL;DR

Go to the Old Man’s study , enter the top-left library path , climb the right-side bookshelves , and you’ll find the Golden Piano upstairs.