Click on the eject button to open the playlist manager. At the left you'll see the content of the directory you were in the last time you edited your playlist. At the right you see your current playlist. Select a midi file on the left to append to the playlist by double clicking on it. Or single click, then click on Add.

The only files shown on the left are midi files. Compressed midi files will not be recognized, unfortunately, so if you've used, say, gzip to compress the files, you'll want to click off the Filter button at the bottom. Then all files become visible. KMidi does not decide whether a file is a midi file or not by looking at the name; instead, it reads a bit of the file to see whether it appears to be a midi file. So there's no need to name your midi files with a .mid suffix.

Toward the bottom of the screen are your current playlists. When you first start, there will be only one, called default with the sample midis from the KMidi distribution. You change the contents of this by clicking once on the name default (if it is not already selected) then clicking File->Save to replace the contents of the playlist file with your current playlist. Or click File->Append to concatenate your current playlist onto the end of a playlist file. To create a new playlist, click File->Save as ... instead and fill in the new name you've chosen into the little box that appears. Double click on the name of a playlist to replace your current playlist with the contents of the one you've saved. This can also be done from the front panel by single clicking on the name of a playlist in the Select Playlist box.

Remove a playlist by clicking on its name, then clicking File->Remove.

The vertical bar separating the directory list from the playlist can be dragged from left to right with the mouse. The horizontal bar separating these from the playlist names can be dragged up and down.

The names of midi files you see on the front panel may differ slightly from the actual file names. For readability, KMidi replaces any “_” in the midi file name by spaces and chops off the .mid/ .MID ending if present.

Clicking the configure button on the panel takes you to a configure screen where you can choose the background color of the panel's two windows and the led color. At the moment, the color used for percussion in the channel meter is not configurable - it's always yellow.

On the bottom panel at the top left you'll find the patchset selector. For KMidi as distributed, you'll see three patchset options: piano + guitar, piano, and guitar. There isn't any real point to selecting the piano or guitar patchsets; the choices are there merely as an illustration. When you acquire a bunch of patchsets, you can set things up so as to switch between them from the panel. Here is how to do that:

For each patchset, create a cfg file describing the patches and their banks and instrument (midi program) numbers. Then in the file timidity.cfg, enter a line source filename and a preceding line if n, where filename is the name you gave to the file describing the patches, and n is the line where filename will appear in KMidi's panel in the select patchset box. Clicking on this name will select the patchset. The numbering of the patchsets starts with number 0.

In cfg files, the banks/drumsets and names of patches must be given, since those that are not declared will not be loaded from files (GUS patch files or sound fonts) even though the patches are available. This way it's easy to exclude certain patches from a sound font so as to load better ones from a subseqently loaded font. Just don't declare them before you've asked to load the font.

When the same patch of the same bank or drumset is declared more than once, only the first declaration counts. So put your best fonts first.

There is a utility sf2cfg to construct a cfg file for a sbk/sf2 sound font, which spits out all the patches that are present in the font. Also, I've included sample cfg files for chaos8m.sf2 and chaos12m.sf2.

Do you hear dropouts in the music? It's possible for KMidi to get behind in doing the many calculations required to adjust the pitch of instrument patches, filter the signal, combine notes, and so on. If this happens, you may be able to improve the situation by using the spinbox on the lower panel to the right. This adjusts the maximum number of polyphonic “voices” used at the same time. When you lower the maximum polyphony, you lighten KMidi's burden at the cost of some chorus or reverb effect being lost, or some notes being cut short or actually being omitted altogether. (In some circumstances, KMidi generates extra notes to approximate the effect of midi chorus and reverberation.)

Effects modify the sound in various ways, some of which I'm not too clear about. There are four ways effects may be requested and two ways you can control them.

A midi song may specify an effect for all the instruments playing on any particular one of the 16 midi channels. Or, it may specify several effects for several channels. When you click down the panel's eff button, the signal is filtered to approximate the midi effects: chorus, reverberation, celeste, and phaser. But there won't be any effects unless the song in the midi file asks for them. Two of the standard midi effects, harmonics and brightness, are not yet implemented by filters. (The filters were coded by Nicolas Witczak.)

When you don't click down the eff button, you still get some chorus and reverberation on channels where it's requested, but it's done in a different way. Now, instead of using filters, extra notes are generated. They are detuned slightly for chorus effect and delayed slightly for reverberation. There are also some adjustments made to note envelopes and vibrato. With eff turned off, you get no channel celeste or phaser effects.

A second way effects may be requested is by a patch. That is, an instrument patch may contain a suggested chorus and/or reverb level. AWE patches generally do specify effects, but Gravis-Forte patches don't. (That's why AWE patchsets tend to sound a bit fruity.) Effects requested this way are done by the ghost note method, and are unaffected by the eff button.

Thirdly, you may request effects. Notice the four checkboxes at the right of the panel. Each has three states: normal (the default), extra, and off. The middle two checkboxes control chorus and reverb. If they are set to normal, effects are treated as described above. Set to extra, extra notes are generated for chorus or reverb for all instruments and all channels, and this is in addition to the effects filters if they are requested by clicking eff. When they are set to off, no extra chorus or reverb notes are generated.

Finally, effects may be requested by midi system exclusive message in a midi file -- “sysexes”. These are intended to control the hardware of specific synthesizers. KMidi does a certain amount of decoding of sysexes for Roland GS synths and Yamaha XG synths and does its best to modify the sound accordingly. Chorus, reverb, and variations on these are done by the “ghost note” method and can be switched off with the checkboxes just mentioned. However, when the celeste variation of chorusing is requested in an XG sysex, this invokes Witczak's celeste filter, provided the eff button is clicked on.

Except for giving the names of one or more midi files on the command line, the material in this section is probably not very useful to know about. If you have a need for these options, you'd probably prefer to use the command line version of this program: timidity.

Use "-" as filename to read a MIDI file from stdin

TiMidity has a tone generator, two envelope generators, three low frequency sine-wave oscillators, a low pass filter, and an effects unit. (The low pass filter is used only when KMidi's fourth interpolation option is chosen and the on filt button is depressed -- at present it doesn't work well.)

The tone generator resamples instrument patches at the basic frequencies appropriate for specific notes being played. (The interpolation algorithm used is selectable using the four checkboxes on the upper panel.)

The envelope generators modulate each note with successively: an attack phase, a hold phase, a decay, and a release. One of the generators affects amplitude, and the other affects pitch and/or the cutoff frequency of the low pass filter.

The low frequency oscillators modulate amplitude (for tremolo), frequency (for vibrato), and the low pass filter cutoff frequency (XG “rezo sweep”).

The effects unit supplies echo, detuning, reverberation, chorusing, celeste, and phaser effects. Echo (done by generating extra echo notes) and reverberation (done with a filter) implement midi reverberation. Detuning (done by generating extra pitch bent notes) and chorusing (done with a filter) implement midi chorusing. (The effects filters are active only when KMidi's eff button is pressed on. Echo and detuning can be controlled with the middle two checkboxes on the right of the lower panel and from the Chorus and Reverb menus.)

Instruments may have either one or two tone elements, and for each of these, a patch set may provide separate patches for different note-velocity ranges (commonly for pianos) and for different note-pitch ranges. GUS patch sets, however, provide only one tone element and one velocity range per instrument. (If you click the rightmost checkbox at the right of the lower panel, KMidi will display in its info window the names of patches as it loads them, a (2) if they have two tone elements, and the velocity range.)

Almost all midi messages and controllers that I'm aware of are implemented somehow (meaning that they cause something to happen, if not necessarily the right thing). NRPN controllers for setting attack and decay time are not implemented, because I haven't found any midi files that use them. The flanging controller is not implemented (though flanging requested in an XG sysex dump is implemented). Only a few of the hardware oriented controls in Roland and Yamaha system exclusive dumps are implemented.

TiMidity can handle midi files meant to play on up to four synthesizers, keeping separate the four sets of 16 channels for each synth. However, in the midi file, the synths have to be selected using port commands (in either Roland-GS or Yamaha-XG sysex dumps). Some midi files intended for multiple synths don't have port commands. (The info window shows port commands when present.)

The KMidi vertical-bar display of channel activity is limited to two sets of 16 channels. The channel chart of patches with horizontal bars for controller values is limited to just one set of 16 channels.

I've reduced the volumes levels TiMidity generates quite a lot, as compared with the original implementation. This minimizes clipping and gives an increased dynamic range. (There may be some artifacts now at low volumes, unfortunately.) If you need more volume, I suggest you turn up the volume somewhere else, either use KMix to turn up the line volume, the mixer volume for /dev/dsp, or turn up earphones, amplified speakers, or whatever.

TiMidity can fall behind in computing data to send out to the sound driver, and then there are dropouts in the music. TiMidity tries to anticipate the possibility of a dropout by monitoring the state of its output buffer and those of the sound driver, and when there is not much in the buffers, it tries to catch up by minimising the calculations it has to do: it uses a cruder interpolation routine in resampling, stops doing extra echo and detuned notes for reverb and chorus effects, and starts terminating notes early, or even skipping notes altogether. So, depending on midi song, patchset, how fast your system is, even if you don't hear dropouts, you will notice a loss in quality as TiMidity gets busier. KMidi's front panel lights give some picture of how desperate TiMidity is becoming in its effort to keep the music playing. (Signs of desperation: the buffer led goes from healthy greenish to busy orangeish, the interpolation led turns off (meaning linear interpolation is being used for resampling), the echo led goes off, or the detuning led goes off (meaning no extra echo or detuned notes are being played).

Monitoring the output buffer involves calling the sound driver to find out how much data it has buffered up. I know how to do this for Hannu Savolainen's OSS driver (Linux® and some other systems), perhaps for older Suns (it used to work), but not for other drivers.

You can lighten TiMidity's computational burden by various maneuvers:

Of course, there is generally some attendant loss in quality. Having the filt button on doesn't cost anything unless you've also chosen the cspline + filter interpolation option.

It's possible for TiMidity to use an excessive amount of memory for patches. Symptoms are your window system becoming very sluggish, or crashing. This is probably only a problem when using big sf2 soundfonts of 30+ megabytes. For instance, the piano patches in Personal Choice's PC400 soundfont can occupy 25 megs each. After playing a list of midi files which use three of these pianos, well, that's 75 megs of ram right there. In its configuration dialog, KMidi lets you set a maximum number of megs to be used to keep patches used in playing previous midi files; when this maximum is exceeded, TiMidity will unload least recently used patches, returning ram to the system. The default maximum is 60 megs, which works ok on my system (I have 48 megs ram and 196 megs cache). Setting this to a lower value means that more patches have to be reloaded from patch files as you play through a list of midi songs, which slows things up. If you're ram rich, you can set it to no limit.

If you allowed enough room, entire soundfont files are read at once, instead of patch by patch. Setting the maximum too low can be counterproductive, because soundfont files occupy much less memory in toto when the entire file is read than when the patches are read individually (I don't know why).

For little-endian systems like x86, rather than being read in, sf2 soundfonts are mmapped. This is much faster on startup. I haven't figured out a way to do this for big-endian systems.

After playing each midi file, KMidi will report in the info window on how much memory is currently occupied by patches.

If you don't have much ram or cache memory, setting a low maximum for patch memory might not prevent KMidi from crashing your system. So be careful using big soundfonts.