All goat horns display as Ponder goat horns and play the Ponder instrument. This may possibly be caused by goat horns ignoring the instrument data since a blank goat horn and goat horns with an invalid instrument also play Ponder and display as Ponder and MC-252773 was recently fixed.

Steps to reproduce:

   Method 1:

• Take a goat horn from the creative inventory besides the first one (the real Ponder)
• Observe the display tooltip and instrument sound
  • Displays as Ponder and plays the Ponder instrument
• Run the command [ /data get entity @s SelectedItem.tag.instrument ] while holding the goat horn
  • Returned information displays the correct instrument data

   Method 2:

• Obtain the Sing goat horn by running [ /give @s minecraft:goat_horn{instrument:"minecraft:sing_goat_horn"} ]
• Observe the display tooltip and instrument sound
  • Displays as Ponder and plays the Ponder instrument
  • Since the goat horn shows "Tools and Utilities" in it's tooltip, it's the corresponding Sing goat horn in the creative inventory