I installed the ‘audio/mad’ port which can convert MP3 to PCM:
moe# madplay -v -o raw:Entropy.pcm Entropy.mp3
MPEG Audio Decoder 0.14.2 (beta) - Copyright (C) 2000-2001 Robert Leslie
Title: Entropy
Artist: MC Hawking
Album: A Brief History of Rhyme
Year: 1994
Genre: Rap
Comment: www.mchawking.com
00:03:21 Layer III, 128 kbps, 44100 Hz, joint stereo (MS), no CRC
7722 frames decoded (0:03:21.7), +0.2 dB peak amplitude, 7 clipped samples
Then to burn them to a CD:
moe# burncd -f /dev/acd0a audio mighty.pcm emchawking.pcm creation.pcm crazy.pcm LedZeppelinMedley.pcm JesseHelms.pcm Entropy.pcm fixate
next writeable LBA 0
writing from file mighty.pcm size 20664 KB
written this track 20664 KB (100%) total 20664 KB
next writeable LBA 9149
writing from file emchawking.pcm size 36306 KB
written this track 36306 KB (100%) total 56971 KB
next writeable LBA 25108
writing from file creation.pcm size 24408 KB
written this track 24408 KB (100%) total 81380 KB
next writeable LBA 35887
writing from file crazy.pcm size 24304 KB
written this track 24305 KB (100%) total 105686 KB
next writeable LBA 46621
writing from file LedZeppelinMedley.pcm size 54301 KB
written this track 54302 KB (100%) total 159988 KB
next writeable LBA 70415
writing from file JesseHelms.pcm size 33480 KB
written this track 33481 KB (100%) total 193470 KB
next writeable LBA 85144
writing from file Entropy.pcm size 34749 KB
written this track 34749 KB (100%) total 228219 KB
fixating CD, please wait..