mpd with bluetooth speaker has no sound

My environment has two audio output: HDMI and Bluetooth speaker. Usually both of them work correctly. For example, #this plays sound via bluetooth speaker $ aplay -D default jingle.wav #this plays sound via HDMI $ aplay -D plughw:1,7 jingle.wav However, mpc play doesn't play any sound. My /etc/mpd.conf is a default one except for the music directory. So music_directory "smb://xxx.xxx.xx.x/some_directory" ... audio_output { type "alsa" name "My ALSA Device" # device "hw:0,0" # optional # mixer_type "hardware" # optional # mixer_device "default" # optional # mixer_control "PCM" # optional # mixer_index "0" # optional } I use a remote music directory (smb protocol) and the connection is ok. According to man mpd.conf, the default value of device field is "default". But mpc play plays no sound though I expect it plays via the bluetooth speaker as the aplay -D default command above. sudo mpd --no-daemon --stderr says exception: OutputThread could not get realtime scheduling, continuing anyway: sched_setscheduler failed: Operation not permitted avahi: Service 'Music Player' successfully established. client: opened from xxx.x.x.x:xxxxx No protocol specified xcb_connection_has_error() returned true No protocol specified No protocol specified xcb_connection_has_error() returned true exception: Failed to read mixer for 'My ALSA Device': no such mixer control: PCM The last line may be the cause, so I set the mixer_type field as "none". But still no sound. mpc play successes and the current position (e.g. 00:56/3:20 (58%)) progresses but no sound. How can I use my bluetooth speaker? If I set device to plughw:1,7, mpc play actually plays sound via HDMI as the aplay command above. However, I would like to use the bluetooth speaker. Environment: $ lsb_relase -d Description: Linux Mint 19 Tara $ mpd --version Music Player Daemon 0.20.18 I installed mpd via sudo apt install mpd.