I just wanted to report that this NSF file from the Super Mario Bros. 3 page on ocremix.org seems to have a broken DPCM track. I played back some songs from the NSF in foobar2k (via foo_gep) and also imported it into Famitracker. Both play only garbled noise instead of a DPCM-drumtrack. There are other NSF rips of Maro 3s music around that play back without issues and clean drums, so I suppose the NSF file is a bad dump and should be replaced.