* installing *source* package ‘fluidsynth’ ...
** using staged installation
Package fluidsynth was not found in the pkg-config search path.
Perhaps you should add the directory containing `fluidsynth.pc'
to the PKG_CONFIG_PATH environment variable
Package 'fluidsynth', required by 'virtual:world', not found
Using PKG_CFLAGS=
Using PKG_LIBS=-lfluidsynth
--------------------------- [ANTICONF] --------------------------------
Configuration failed because fluidsynth was not found. Try installing:
 * deb: libfluidsynth-dev (Debian, Ubuntu, etc)
 * rpm: fluidsynth-devel (Fedora, EPEL)
 * brew: fluidsynth (OSX)
If fluidsynth is already installed, check that 'pkg-config' is in your
PATH and PKG_CONFIG_PATH contains a fluidsynth.pc file. If pkg-config
is unavailable you can set INCLUDE_DIR and LIB_DIR manually via:
R CMD INSTALL --configure-vars='INCLUDE_DIR=... LIB_DIR=...'
-------------------------- [ERROR MESSAGE] ---------------------------
<stdin>:1:10: fatal error: 'fluidsynth.h' file not found
    1 | #include <fluidsynth.h>
      |          ^~~~~~~~~~~~~~
1 error generated.
--------------------------------------------------------------------
ERROR: configuration failed for package ‘fluidsynth’
* removing ‘/srv/hornik/tmp/CRAN/fluidsynth.Rcheck/fluidsynth’