diff --git a/README.md b/README.md
index 70d39bc..6c30f78 100644
--- a/README.md
+++ b/README.md
@@ -66,9 +66,7 @@ localhost. The app isn't currently set up for that, but it could be.
 
 Backing tracks are 16-bit 1-channel 48k wav files.  You can make one with:
 
-    $ lame --decode input.mp3 intermediate-a.wav && \
-      sox intermediate-a.wav intermediate-b.wav remix 1 && \
-      sox intermediate-b.wav -r 48000 output.wav
+    $ sox input.mp3 -r 48000 output.wav remix 1
 
 This should look like:
 
@@ -108,7 +106,7 @@ sudo apt update
 sudo apt upgrade
 sudo apt install python3-distutils uuid-dev libcap-dev libpcre3-dev \
                  nginx python3-pip emacs letsencrypt opus-tools \
-                 python3-certbot-nginx
+                 python3-certbot-nginx sox libsox-fmt-mp3
 sudo python3 -mpip install uwsgi
 mkdir ~/src
 cd ~/src && git clone https://github.com/gwillen/solstice-audio-test.git
diff --git a/server.py b/server.py
index 5a50fb2..996400d 100755
--- a/server.py
+++ b/server.py
@@ -167,7 +167,7 @@ def clear_whole_buffer():
 # For volume scaling.
 N_PHANTOM_PEOPLE = 2
 
-AUDIO_DIR = os.path.join(os.path.dirname(__file__), "audio")
+
 RECORDINGS_DIRNAME = "recordings"
 RECORDINGS_DIR = os.path.join(
     os.path.dirname(__file__), "html", RECORDINGS_DIRNAME)
@@ -302,7 +302,7 @@ def cleanup_(self):
 
 tracks = []
 def populate_tracks() -> None:
-    for track in sorted(os.listdir(AUDIO_DIR)):
+    for track in sorted(os.listdir(util.AUDIO_DIR)):
         if track != "README":
             tracks.append(track)
     tracks.append(METRONOME)
diff --git a/server_wrapper.py b/server_wrapper.py
index cd5f3bd..0d19653 100755
--- a/server_wrapper.py
+++ b/server_wrapper.py
@@ -5,7 +5,7 @@
 import urllib.parse
 import numpy as np  # type:ignore
 import opuslib  # type:ignore
-import traceback
+import util
 import time
 import struct
 
@@ -252,22 +252,6 @@ def do_GET(environ, start_response) -> None:
     # If we give a 0-byte response, Chrome Dev Tools gives a misleading error (see https://stackoverflow.com/questions/57477805/why-do-i-get-fetch-failed-loading-when-it-actually-worked)
     return b'ok',
 
-def die500(start_response, e):
-    # This is slightly sketchy: this assumes we are currently in the middle
-    #   of an exception handler for the exception e (which happens to be
-    #   true.)
-    trb = traceback.format_exc().encode("utf-8")
-    start_response('500 Internal Server Error', [
-        ('Content-Type', 'text/plain'),
-        ("Access-Control-Allow-Origin", "*"),
-        ("Access-Control-Max-Age", "86400"),
-        ("Access-Control-Expose-Headers", "X-Audio-Metadata"),
-        ("X-Audio-Metadata", json.dumps({
-            "kill_client": True,
-            "message": str(e)
-        }))])
-    return trb,
-
 # POST requests absolutely must have a numeric user_id for all requests which
 #   make it as far as handle_post; such requests must be associated with a user
 #   or there's nothing we can do with them, and they will fail.
@@ -315,7 +299,7 @@ def do_POST(environ, start_response) -> None:
             del users[userid]
         # Log it
         print("Request raised exception!\nParams:", query_string, "\n", traceback.format_exc(), file=sys.stderr)
-        return die500(start_response, e)
+        return util.die500(start_response, e)
 
     combined_data = x_audio_metadata.encode('utf-8') + data
 
diff --git a/upload.py b/upload.py
new file mode 100644
index 0000000..c3e27b5
--- /dev/null
+++ b/upload.py
@@ -0,0 +1,45 @@
+import util
+import tempfile
+import subprocess
+import traceback
+import sys
+
+def decode_and_save(in_data_raw):
+  with tempfile.NamedTemporaryFile() as tmp_upload:
+    tmp_upload.write(in_data_raw)
+    tmp_upload.flush()
+
+    subprocess.check_call([
+      "sox",
+      "-t", "mp3", tmp_upload.name,
+      "-r", "48000",
+      "-t", "wav", util.UPLOAD_FNAME,
+      "remix", "1"])
+
+def application(environ, start_response):
+  try:
+    content_length = int(environ.get('CONTENT_LENGTH', 0))
+    in_data_raw = environ['wsgi.input'].read(content_length)
+
+    query_string = environ['QUERY_STRING']
+
+    if len(query_string) > 0:
+      query_params = urllib.parse.parse_qs(query_string, strict_parsing=True)
+    else:
+      query_params = {}
+
+      decode_and_save(in_data_raw)
+
+      start_response('200 OK', [("Content-Type", "text/plain")])
+      return b"ok",
+  except Exception as e:
+    print("ERROR:", query_string, "\n", traceback.\
+          format_exc(), file=sys.stderr)
+    return util.die500(start_response, e)
+
+def serve():
+  from wsgiref.simple_server import make_server
+  make_server(b'',8082,application).serve_forever()
+
+if __name__ == "__main__":
+  serve()