diff --git a/build_clips.py b/build_clips.py
index 6c2a66a..3544db5 100644
--- a/build_clips.py
+++ b/build_clips.py
@@ -1,11 +1,10 @@
 import sqlite3
 import os
 import glob
-import subprocess
 import shutil
+import sox
 
 shutil.rmtree('clips')
-# os.removedirs('clips')
 os.mkdir('clips')
 
 db = sqlite3.connect("file:songbook.sqlite?mode=ro", uri=True)
@@ -40,29 +39,36 @@ for song, motif, start, duration in db.execute('''
 
     destination = f'clips/{song:04}-{motif:03}.flac'
 
-    print (destination)
+    print(destination)
+
+    source_duration = sox.file_info.duration(source)
 
     # trim and fade start
 
-    if start / 1000 < 2:
+    if start < 2:
         trim_start = 0
-        trim_duration = duration / 1000 + start / 1000 + 2
         fade_in = 0
-        fade_out = 2
     else: 
-        trim_start = start / 1000 - 2
-        trim_duration = duration / 1000 + 4
+        trim_start = start - 2
         fade_in = 2
-        fade_out = 2
 
     # trim and fade end (to be continued)
 
-
+    if source_duration - (start + duration ) < 2:
+        trim_end = None
+        fade_out = 0
+    else:
+        trim_end = start + duration + 2
+        fade_out = 2
 
     # call sox
 
-    sox_args = [str(x) for x in ["sox", source, destination,
-                "trim", trim_start, trim_duration,
-                "fade", "t", fade_in, "-0", fade_out]]
-    print(' '.join(sox_args))
-    subprocess.run(sox_args, check = True)
\ No newline at end of file
+    tf = sox.Transformer()
+    tf.trim(trim_start, trim_end)
+    tf.fade(fade_in, fade_out, 't')
+    sox_status = tf.build_file(source, destination, return_output=True)
+
+    # error check
+
+    if sox_status != (0, '', ''):
+        print(sox_status)
\ No newline at end of file
diff --git a/db.sql b/db.sql
index 3d993dc..7e15673 100644
--- a/db.sql
+++ b/db.sql
@@ -1,7 +1,9 @@
+PRAGMA foreign_keys = ON;
+
 create table song(
     id int primary key,
     name text not null,
-    name_jp text,
+    name_jp text not null,
     unique(name,name_jp)
 );
 
@@ -15,7 +17,7 @@ create table album(
 create table artist(
     id int primary key,
     name text not null,
-    name_rm text
+    name_rm text not null
 );
 
 create unique index ix_artist_name on artist(
diff --git a/reference.ods b/reference.ods
index d23a999..3bee5a0 100644
Binary files a/reference.ods and b/reference.ods differ
diff --git a/reference_clips.ods b/reference_clips.ods
index cc11f87..219c1af 100644
Binary files a/reference_clips.ods and b/reference_clips.ods differ