Number of cell
|Instrument number
||Effect data
|| /|
2G533FF
/\|
||Effect number
||
Note and octave

For this note, it's #2 of 63 in the pattern, it's a G in octave 5,
using instrument number 3, effect 3, and data FF. What effect 3
actually means depends on the tracker in question. On SoundSmith and
derivatives, it means "Set the volume to --", in this case set it to
$FF (255) which is the maximum.

Now, into a larger structure. 64 lines of cells makes up a block, or
pattern as it is sometimes called. (some Amiga and PC editors allow
blocks of varying lengths, but we won't consider those here). You can
terminate a block early with a special effect. On most trackers, an
actual effect number is used. On SoundSmith, entering the note/octave
as NXT makes that line of cells the last line played in that block.

Now that we've covered cells and blocks, we can get into the
large-scale structure of things. To make a complete song, we can give
the player a 'block list' which tells it to play a specific sequence
of blocks in a specific order. For instance, we could have it play
block 4, then block 0, then block 1, then block 2, then block 2. An
entry in the block list is known as a 'position'. MOD-derived formats
typically allow 128 positions, and 64 (MOD) or 71 (SoundSmith) blocks.

For those of you with (gasp!) other machines and more modern trackers,
you'll notice many of these trackers have a 4th column in each track.
The extra column is usually a volume level for the track, where 0
means "don't change" and all other values do - this helps to preserve
effects and make things more flexible. Also, nearly all limits
associated with the original MOD format are no longer in force -
Impulse Tracker on the PC, probably the most advanced tracker
available today, offers 64 tracks, up to 32 megabytes of samples, and
nearly unlimited blocks and positions.

A Practical Example:

Crank up MODZap 0.9 or later and a favorite tune. Set it to the
"Classic Player". Now, remember those numbers you never understood
before, off to the left of the scrolling cells? Here's what they mean,
in terms of what you just learned: *grin*

This is the # of entries in the block list>35--- 0000
This is the current block list entry playing>04--- 0000
This is the block # currently playing>01--- 0000
This is the current cell # in the current block >36A#4 0384

As you watch, the current cell # will normally (barring certain
effects) smoothly go from 00 to 63. When it hits 63, it will go to 00
again and the current block list entry number will increment by 1.
When it does, the current block number will change if needed
(remember, a block can appear multiple places in the block list).