Description:
Shared library libcarla_native-plugin.so missing, no audio when editing track.
Possibly carla (community package, part of group pro-audio) should be added as a package dependency.

Additional info:
When I manually install carla package from community I do have working audio.
$ pacman -Qi lmms
Name : lmms
Version : 1.2.0-3
Description : The Linux MultiMedia Studio
Architecture : x86_64
URL : https://lmms.io
Licenses : GPL2
Groups : pro-audio
Provides : None
Depends On : fftw fltk fluidsynth lame libgig libsamplerate qt5-x11extras sdl stk
Optional Deps : pulseaudio: pulseaudio support [installed]
wine: VST plugin support
Required By : None
Optional For : None
Conflicts With : None
Replaces : None
Installed Size : 34.23 MiB
Packager : David Runge <dave@sleepmap.de>
Build Date : Mon 29 Jul 2019 03:36:20 PM CEST
Install Date : Wed 09 Oct 2019 10:30:21 PM CEST
Install Reason : Explicitly installed
Install Script : No
Validated By : Signature

Steps to reproduce:
- Start a minimalist installation of Arch Linux (e.g. archlinux/archlinux vagrant box)
```
vagrant init archlinux/archlinux
vagrant up
```
- Install minimalist WM and lmms and lanch WM
```
sudo pacman -S xorg xorg-drivers xf86-video-fbdev fluxbox sx xterm lmms
which startfluxbox > ~/.local/sx/sxrc
chmod 740 ~/.local/sx/sxrc
sx
```
- On my system X refused to start with virtualbox-guest-modules-arch installed. If so, install virtualbox-guest-dkms
```
sudo pacman -S virtualbox-guest-dkms
reboot
sx
```
- From WM start a terminal (e.g. xterm)
- From terminal, launch lmms and notice the errors about libraries that can't be loaded
```
lmms
Cannot load library /usr/lib/lmms/libcarlarack.so: (libcarlabase.so: cannot open shared object file: No such file or directory)
Cannot load library /usr/lib/lmms/libcarlapatchbay.so: (libcarlabase.so: cannot open shared object file: No such file or directory)
Cannot load library /usr/lib/lmms/libcarlabase.so: (libcarla_native-plugin.so: cannot open shared object file: No such file or directory)
```