tce-load -i compiletc meson itstool gobject-introspection-dev libdazzle-dev libmediaart-dev tracker3-dev grilo-dev gtk3-gir py3.6gobject-dev desktop-file-utils appstream-glib gettext grilo-plugins-dev

wget https://download.gnome.org/sources/gnome-music/40/gnome-music-40.0.tar.xz
https://gitlab.gnome.org/GNOME/gnome-music/-/commit/b710b1b66a053ef04c011adc0a566ff2a12e1f32.diff
https://gitlab.gnome.org/GNOME/gnome-music/-/commit/54dd7286338a509acb4f4ce9a8072dcc395c9e48.diff

cd gnome-music-40.0

patch -R  -i ../gnome-music.patch
patch -R  -i ../gnome-music1.patch

mkdir build
cd build

CC="gcc -flto -mtune=generic -Os -pipe" CXX="g++ -mtune=generic -Os -pipe -fno-exceptions -fno-rtti" meson --prefix=/usr/local --localstatedir=/var --buildtype=plain

ninja [0m 6.31s]
sudo ninja install

runtime gstreamer-gir libmediaart-gir tracker2-gir libdazzle-gir gst-plugins-good

$ gnome-music
Traceback (most recent call last):
  File "/usr/local/bin/gnome-music", line 132, in <module>
    sys.exit(main())
  File "/usr/local/bin/gnome-music", line 127, in main
    return run_application()
  File "/usr/local/bin/gnome-music", line 113, in run_application
    from gnomemusic.application import Application
  File "/usr/local/lib/python3.6/site-packages/gnomemusic/application.py", line 37, in <module>
    from gnomemusic.coregrilo import CoreGrilo
  File "/usr/local/lib/python3.6/site-packages/gnomemusic/coregrilo.py", line 31, in <module>
    from gnomemusic.grilowrappers.grlsearchwrapper import GrlSearchWrapper
  File "/usr/local/lib/python3.6/site-packages/gnomemusic/grilowrappers/grlsearchwrapper.py", line 29, in <module>
    from gnomemusic.coresong import CoreSong
  File "/usr/local/lib/python3.6/site-packages/gnomemusic/coresong.py", line 25
    from __future__ import annotations

SyntaxError: future feature annotations is not defined

Looking at your error traceback, it looks like you are using python 3.5. Is that the case?

If so, then the error happens because according to PEP-563 the import of __future__ annotations is available starting with Python 3.7

https://pypi.org/project/future-annotations/

$ sudo pip3.6 install future-annotations
Requirement already satisfied: future-annotations in /usr/local/lib/python3.6/site-packages (1.0.0)
Collecting tokenize-rt>=3
  Downloading tokenize_rt-4.1.0-py2.py3-none-any.whl (6.1 kB)
Installing collected packages: tokenize-rt
Successfully installed tokenize-rt-4.1.0