MPD (music player daemon) is an audio player that has a server-client
architecture.  It plays audio files, organizes playlists and maintains a music
database, all while using very few resources. In order to interface with it, a
separate client is needed. 

OP's choice falls on   vimpc, but you may prefer the more popular ncmpccp, a
graphical client like GMPC  or Cantata, or a Web frontend like ympd. All those
are available on pkgsrc. 

This tutorial will also show how to bind volume and multimedia keys in CTWM,
and how to set up custom desktop notifications for terminal clients, thus to
show the currently playing track and the relevant album cover. 

Note: This tutorial assumes mpd to be run as a user process (not as a rc
service).

■ Preliminary tasks:
 
1. install: 
 - audio/musicpd
 - audio/mpc (cli-client, required for bindings)
 - audio/vimpc (or other client)

2. place you music inside the desired folder (here we'll use ~/Music)

3. prepare mpd's directory:

$ mkdir -p ~/.mpd/playlist
$ for f in db log pid state stick; do
    > touch ~/.mpd/${f}
    > done

4. Configure MPD. Edit a ~/.mpd/mpd.conf file as follows. We will use SunAudio (audio(4)) as backend. 

music_directory        "~/Music"
playlist_directory     "~/.mpd/playlist"
log_file               "~/.mpd/log"
pid_file               "~/.mpd/pid"
state_file             "~/.mpd/state"
sticker_file           "~/.mpd/stick"
bind_to_address        "127.0.0.1"
port                   "6600"
max_connections        "5"
auto_update            "yes"
mixer_type             "software"
filesystem_charset     "UTF-8"

database {
        plugin          "simple"
        path            "~/.mpd/db"
}

audio_output {
       type             "solaris"
       name             "sunaudio"
       device           "/dev/audio"
}

# optional, only needed for visualizers
# adjust the fifo path to something user-writable
audio_output {
    type                "fifo"
    name                "my_fifo"
    path                "/tmp/run/1000/mpd.fifo"
    format              "44100:16:2"
}

5. environment

MPD_HOST="127.0.0.1"
MPD_PORT="6600"
MPC_FORMAT="%title% \n%artist% - %album%"

■ First run 
First run mpd in foreground to check everything is in place. 
mpd shall scan the music directory for songs and add them
to the database

$ mpd --no-daemon --verbose --stderr

If anything went right you can add `/usr/pkg/bin/mpd &` to your X startup script.

Testing playback
With mpd running in background this time, let's test playback using the `mpc` client.

$ mpc searchadd title "satellite of love"
$ mpc play
Satellite of love 
The Velvet Underground - 
[playing] #1/1   0:00/3:43 (0%)
volume:100%   repeat: off   random: off   single: off   consume: off

■ Using vimpc
Edit a ~/.vimpcrc file as follows:

echo Parsing config file

"-- colours 
" hi <prop> <bg> <fg>
hi tab default white
hi status default white
hi current default green
hi id default yellow
hi pager default magenta
hi error default red
hi progress default cyan

"-- settings
" default tab
set window playlist
" tabs to open upon startup
set windows help,library,browse,playlist
" stop playing music upon exiting
set stoponquit
set autoscroll
set colour
"highlight search result
set hlsearch
"wrap search results
set searchwrap
"case insensitive searching
set ignorecase
set sortignorethe
set sortignorecase
set mouse
set local-music-dir ~/Music
set libraryformat %n \| {%t}|{%f}$E$R $H[$H%l$H]$H
set songformat {%a - %b - %t}|{%f}$E$R [%l]
" set songformat {%a$A33%b$A66%t}|{%f}$E$R [%l]
" set songformat {%?}|{%f}$E$R $H[$H%l$H]$H
" set songformat {{%?}|{%?}}|{%f}$E$R $H[$H%l$H]$H

"-- bindings 
map q ZQ
map Q ZQ
map <C-N> gt
map <C-P> gT
map gf :browse<C-M>gg/
map gs :shuffle<C-M>
map ga :addall<C-M>:shuffle<C-M>
map gl :load 
map 'a :findartist! 
map 'g :findgenre! 
map 'b :findalbum! 
map <BS> f
map <Space> p

"-- autocmds
" playlist consume
"consume on
" update database 
update
"turn on shuffle
shuffle
"start playing
"play 1

echo Config File Complete

As you can see, vimpc has a strongly vi-influenced command syntax and lexicon.
At this point you can launch the client in a terminal emulator or in wscons
and test it. The first panel is a help screen which will allow you to quickly
become comfortable with the client.

■ Desktop notifications
I use the following `mpdnotify` script, to display the currently playing song
(requires libnotify, ffmpeg and a running notification daemon).

#!/bin/sh

LIBRARY="${HOME}/Music"
ICONPATH="${HOME}/.icons/Sardi-Ghost-Flexible"
DEFAULT_IMG="${ICONPATH}/scalable/apps/gnome-music.svg"
FFMPEG="/usr/pkg/bin/ffmpeg"

if [ -x "$FFMPEG" ]; then \
	ffmpeg -y -i "$(mpc --format "$LIBRARY"/%file% \
	| head -n 1)" /tmp/mpd_cover.jpg > /dev/null 2>&1
else
	notify-send -u critical "ffmpeg not found"
fi

[ -n "$DBUS_SESSION_BUS_ADDRESS" ] && \
	notify-send -u low -i /tmp/mpd_cover.jpg "Now Playing ♫" \
	"$(mpc --format "%title% \n%artist% - %album%" current)" || \
	notify-send -u low -i $DEFAULT_IMG "Now Playing ♫" \
	"$(mpc --format "%title% \n%artist% - %album%" current)"

The following `vol` script displays the current volume level (percentage)  as
a desktop notification.

#!/bin/sh
VOL=$(mixerctl -n outputs.master | cut -d , -f 1 | \
     awk '{print $1/254*100}' | cut -d . -f 1)
notify-send "volume: $VOL %

■ Volume and multimedia keys bindings in CTWM
Inside your ~/.ctwmrc, you may add:

# scripts path
define(`bindir',`/home/_logname_/.bin')

# Now playing
"s" = m4         : all : f.exec "bindir/mpdnotify &"

# Volume keys
"XF86AudioLowerVolume" = : all : f.exec "mixerctl -w outputs.master-=3,3 ; sh bindir/vol"
"XF86AudioRaiseVolume" = : all : f.exec "mixerctl -w outputs.master+=3,3 ; sh bindir/vol"
"XF86AudioMute"        = : all : f.exec "mixerctl -w outputs.master.mute=on ; sh bindir/vol"

# Multimedia Keys
"XF86AudioPlay" = : all : f.exec "mpc play  > /dev/null 2>&1 ; sh bindir/mpdnotify"
"XF86AudioStop" = : all : f.exec "mpc pause > /dev/null 2>&1 ; notify-send 'playback stopped'"
"XF86AudioPrev" = : all : f.exec "mpc prev  > /dev/null 2>&1 ; sh bindir/mpdnotify"
"XF86AudioNext" = : all : f.exec "mpc next  > /dev/null 2>&1 ; sh bindir/mpdnotify"

This:
- will bind volume keys to a suitable mixerctl command which lowers or
  increases volume by 3% and triggers the `vol` script. 
- will bind multimedia keys to suitable mpc commands and trigger desktop
  notifications by invoking the `mpdnotify` script.