MODPLUG_RESAMPLE_NEAREST sounds better for chiptunes.

mpd-chiptunes.diff

diff -rupN mpd-0.17.5.old/src/decoder/modplug_decoder_plugin.c mpd-0.17.5.new/src/decoder/modplug_decoder_plugin.c
--- mpd-0.17.5.old/src/decoder/modplug_decoder_plugin.c	2013-08-01 00:15:41.000000000 -0700
+++ mpd-0.17.5.new/src/decoder/modplug_decoder_plugin.c	2013-10-04 21:36:17.978427703 -0700
@@ -108,7 +108,7 @@ mod_decode(struct decoder *decoder, stru
 
 	ModPlug_GetSettings(&settings);
 	/* alter setting */
-	settings.mResamplingMode = MODPLUG_RESAMPLE_FIR; /* RESAMP */
+	settings.mResamplingMode = MODPLUG_RESAMPLE_NEAREST; /* RESAMP */
 	settings.mChannels = 2;
 	settings.mBits = 16;
 	settings.mFrequency = 44100;