Just search for MIDI sequencer and you'll most likely find one that suits your needs. There are several sequencers that can create MIDI files. doom2.wad) as several ports will either no longer work properly or even start, with altered IWADs. Make sure that you do not alter or edit your IWAD (e.g. Double click on that and open the MIDI file that you renamed in the previous step. At the bottom of the screen you will see a tab that says music. See music for a list of names used on other map slots. If your map occupies the MAP01 slot, you will have to rename the MIDI file to D_RUNNIN for it to work properly.a MIDI file that you want in your level.
