Play the sound of Pi
Python 2, 182 bytes

x=p=6637
while~-p:x=p/2*x/p+2*10**999;p-=2
s=&quot;MThd\0\0\0\6\0\1\0\1\342\4MTrk\0\0\13\301\0\220&quot;
for i in`x`:s+=&quot;JHGECA@&gt;&lt;L\260&quot;[~ord(i)%29]+'{&lt;'
open('p.mid','w').write(s+&quot;\0\377/\0&quot;)

`x` will produce 31415926...20198L. The trailing L is used to produce the final channel message byte, via the mapping ~ord(i)%29.
Outputs a single track Type 1 Midi file, named p.mid to the current working directory.
0000: 4d 54 68 64 00 00 00 06  MThd....  # Midi header, 6 bytes to follow
0008: 00 01 00 01              ....      # Type 1, 1 track
000c: e2 04                    â.        # (-)30 ticks per beat, 4 beats per second

000e: 4d 54 72 6b 00 00 0b c1  MTrk...Á  # Track header, 3009 bytes to follow
0016: 00 90 40 7b              ..@{      # Wait  0 ticks, play E4 (3), 97% volume
001a: 3c 3c 7b                 &lt;&lt;{       # Wait 60 ticks, play C4 (1), 97% volume
001d: 3c 41 7b                 &lt;A{       # Wait 60 ticks, play F4 (4), 97% volume
0020: 3c 3c 7b                 &lt;&lt;{       # Wait 60 ticks, play C4 (1), 97% volume
0023: 3c 43 7b                 &lt;C{       # Wait 60 ticks, play G4 (5), 97% volume
...
0bcf: 3c b0 7b 3c              &lt;°{&lt;      # Wait 60 ticks, all notes off
0bd3: 00 ff 2f 00              .ÿ/.      # End of track marker