diff --git a/examples/chopin.rb b/examples/chopin.rb
index 9197803..90c637b 100644
--- a/examples/chopin.rb
+++ b/examples/chopin.rb
@@ -101,7 +101,7 @@ def score
 final.transpose(12)
 end
 
-SMFWriter.new(:tempo => 80).
+SMFWriter.new(:tempo => 40).
   track(score, :name => 'Op. 20, No. 2').
   save('chopin-op28-no20')
 
diff --git a/lib/music/smf_writer.rb b/lib/music/smf_writer.rb
index 8140307..04930b2 100644
--- a/lib/music/smf_writer.rb
+++ b/lib/music/smf_writer.rb
@@ -8,8 +8,7 @@ class SMFWriter
     def initialize(options = {})
       @time  = MidiTime.new(options.fetch(:resolution, 480))
       @seq   = Sequence.new(1, @time.resolution)
-      @tempo = SetTempo.new(1, bpm_to_qn_per_usec(
-                                   options.fetch(:tempo, 2_000_000)))
+      @tempo = SetTempo.new(1, bpm_to_qn_per_usec(options[:tempo]))
     end
     
     def track(arrangement_or_timeline, options = {})
@@ -49,7 +48,7 @@ def gen_seq_name
       end
       
       def bpm_to_qn_per_usec(bpm)
-        ((bpm/60.0) * 1_000_000).to_i
+        (60_000_000.0 / bpm).to_i
       end
   end
 end