mplayer, vlc and even the horrible Totem would play my music, but my favourite media player — Audacious — wouldn’t. I like Audacious because of its plugins and subtle interface. Some searching around the web didn’t find many solutions except suggesting that the output plugin was incorrect. I managed to fix this by changing from pulseaudio to ALSA in the audio preferences (CTRL+P -> Audio -> Current output plugin). Now I can happily wake my neighbours at 0630 using the excellent Alarm plugin!