With my Sound Card (SB audigy), I had no sequencer (midi) support using the OSS driver.If you own this card (or a SB Live! or similar) I'm afraid you'll have to use the ALSA driver (don't know what Linux distribution you use, but on Suse , you can easily select this in the Yast configuration utility). For Audigy and related cards, for which the midi patches have to be loaded from disk, there are a bit more steps to follow, but this gets off - topic.
hope this helps,

greetings,
J.