It looks like there are two problems:
Garbled/intermittent display on Unicorn HAT/PHAT
On Raspbian 2016-05-10 / NOOBS 1.9.1 booting to X seems to do something with analog audio, where it would have otherwise been left alone and worked, mostly, by sheer luck. You need to force your Pi to HDMI audio using these lines in /boot/config.txt
hdmi_force_hotplug=1
hdmi_force_edid_audio=1
This pretends an HDMI monitor is plugged in, and that it supports audio.
You can also start in CLI mode, which doesn’t load whatever audio stuff is being used in X and has the same effect.
Failed with code -1
If you see something like ws2811_init failed with code -1 this is because you’re running an old version of the rpi-ws281x library on a Pi that it doesn’t recognize. This could be hardware version 0x13 which is a previously unsupported version of the Model B+ as far as I’m aware, or much more likely version 0x900093 which is the Raspberry Pi Zero v1.3 ( new model with camera port )
In this case, the instructions in my post above should work:
sudo pip install -I rpi_ws281x