diff --git a/README.md b/README.md
index 5fcabd2..bc27902 100644
--- a/README.md
+++ b/README.md
@@ -8,35 +8,44 @@ Google cloud account credentials are required. You can specify the filename in a
 ```
 export GOOGLE_APPLICATION_CREDENTIALS=/path/to/serviceaccount/credentials_file.json
 ```
+By default, input is supplied via standard input, but can also be specified from a file with the `-i` option.
+Both plain text and SSML input are supported. Specify `-ssml` to tell the program to expect SSML input from your text source.
 
-Run ```gsquawk -h``` to see the help.
+Output is to a file, but you can set the filename to `-` to send to stdout. This can be useful if you want to convert the file on the fly to a format that gsquawk doesn't support, with **sox** or **ffmpeg** or the like.
+
+Instead of performing TTS, you can use the `-listvoices` option to have gsquawk send you back a list of all available voices. If you run with `-listvoices` and no other options it limits to `en-US` voices, which is the default language selection. You may use the `-l` option along with `-listvoices` to set a specific language code, or use `-l ALL` to give you a list of every voice available in all languages.
+
+Run ```gsquawk -h``` to see the help:
 
 ```
 Usage of ./gsquawk:
   --db float
-        Volume gain in dB. [-96 to 16]
+    	Volume gain in dB. [-96 to 16]
   -f string
-        Audio format selection. MP3 is 32k [mp3,opus,pcm,ulaw,alaw] (default "mp3")
+    	Audio format selection. MP3 is 32k [mp3,opus,pcm,ulaw,alaw] (default "mp3")
   -g string
-        Gender selection. [m,f,n] 'n' means neutral/don't care. (default "m")
+    	Gender selection. [m,f,n] 'n' means neutral/don't care. (default "m")
   -i string
-        Input file path. Defaults to stdin. (default "-")
+    	Input file path. Defaults to stdin. (default "-")
   -l string
-        Language selection. 'en-US', 'en-GB', 'en-AU', 'en-IN',
-        'el-GR', 'ru-RU', etc. (default "en-US")
+    	Language selection. 'en-US', 'en-GB', 'en-AU', 'en-IN',
+    	'el-GR', 'ru-RU', etc. (default "en-US")
+  -listvoices
+    	List available voices, rather than generate TTS. Use in
+    	combination with '-l ALL' to show voices from all languages.
   -o string
-        Output file path. Use '-' for stdout. (default "./tts.mp3")
+    	Output file path. Use '-' for stdout. (default "./tts.mp3")
   -p float
-        Pitch. E.g. '0.0' is normal. '20.0' is highest,
-        '-20.0' is lowest. (default 1)
+    	Pitch. E.g. '0.0' is normal. '20.0' is highest,
+    	'-20.0' is lowest. (default 1)
   -r int
-        Samplerate in Hz. [8000,11025,16000,22050,24000,32000,44100,48000] (default 24000)
+    	Samplerate in Hz. [8000,11025,16000,22050,24000,32000,44100,48000] (default 24000)
   -s float
-        Speed. E.g. '1.0' is normal. '2.0' is double
-        speed, '0.25' is quarter speed, etc. (default 1)
+    	Speed. E.g. '1.0' is normal. '2.0' is double
+    	speed, '0.25' is quarter speed, etc. (default 1)
   -ssml
-        Input is SSML format, rather than plain text.
+    	Input is SSML format, rather than plain text.
   -v string
-        Voice. If specified, this overrides language & gender. (default "unspecified")
-```
+    	Voice. If specified, this overrides language & gender. (default "unspecified")
 
+```