The message that appears when trying to listen to a locked track in the Music Room is the same since Mountain of Faith. However, since Undefined Fantastic Object, it was slightly improved (a comma was added in the second to last row and a fullstop was added at the end of the last two rows).

All digits are closer to the "No." in the unlocked screens.

Minamitsu Murasa's 幽霊「シンカーゴースト」 Phantom "Sinker Ghost" survival spellcard from Undefined Fantastic Object (Normal mode). On Hard and Lunatic the spellcard is called 幽霊「忍び寄る柄杓」 Phantom "Dipper Creeping Close".

Kogasa Tatara's spellcard background became darker in Double Spoiler compared to Undefined Fantastic Object, only to return in Ten Desires to its lighter appearance again.

From the midbosses of Undefined Fantastic Object, only Nazrin from stage 5 has her name shown during the nonspell. However, Nazrin from stage 1 is the only one who doesn't have her name shown during the spellcard.

The red ufos became “more red” in ver. 1.00b of Undefined Fantastic Object. 

Undefined Fantastic Object and Double Spoiler have the same loading animation in the lower right corner. 

Luize & Murasa and Mai & Kogasa share a similar pattern. Thank you @aratanaruu for pointing this out!