A Profile of SoundTracker

The following article is based on a chapter in the author's Linux Music and Sound, published by No Starch Press in October 2000.
Entering Events into a Track

You can insert events into a track by using either your computer's QWERTY keyboard or an external MIDI keyboard. Both methods can be used in either real-time mode (entering and deleting events while the pattern loops) or in step-entry mode (inserting and deleting events one by one, manually incrementing the cursor position). Let's look at the QWERTY method first.

Inserting Events with the QWERTY Keyboard

Event entry is easy with a two-octave span of notes mapped to your computer keyboard as is demonstrated in Table 1.

Table 1. Two-Octave Span of Notes

You can change the starting octave in the Octave scrolling window to the right of the Editing button (see Figure 1).

Click on the Editing button, then use the computer keyboard to audition and insert your instruments (samples) into your tracks. Just click Play Pattern while in Editing mode, and you can insert events in real time while the pattern loops (this method is easier and more accurate at slower tempos). Alternately, you can add events one by one by scrolling to an entry point and inserting sounds in step-entry mode. Events are deleted simply by selecting them with the tracker display cursor (or waiting for the event to scroll by in real time) and hitting the Delete key.

You can use the keyboard in other ways as well. Controls are available for song or pattern play, and nearly all the editing functions. The combined keyboard/mouse interface is easy to master, and you'll quickly be able to compose in SoundTracker with ease. (See Table 2 for a list of the keyboard accelerators.)

Table 2. Keyboard Applications

Inserting Events with a MIDI Keyboard

If your Linux sound system utilizes the ALSA drivers, and if you have configured SoundTracker for ALSA support, you can use an external MIDI keyboard to enter events. MIDI input is basically identical to the QWERTY method. However, you'll need to configure SoundTracker for MIDI input.

Open the Settings/MIDI Configuration menu from the top menu bar. Clicking the Volume button lets SoundTracker use the MIDI velocity value for the volume of the inserted event. Clicking on the channel button locks MIDI input to a particular track, so that MIDI Channel 1 equals Track 1, MIDI Channel 2 equals Track 2 and so forth. If you select the MIDI channel button, you must change the MIDI Out channel on your keyboard to input data to another track. If you leave the button unchecked, you can simply use the Tab or Shift-Tab keys to select a track for recording (i.e., you won't need to change your MIDI Out setting on your keyboard). Set the client and port numbers if necessary (the defaults work fine for me).

Tracking a Module

Tracking (i.e., creating a module) in SoundTracker is a simple five-step process:

  1. Set your pattern number and length with the controls in the upper-left block of the display.

  2. Click on the Editing radio button and select Instrument 1 in the global section.

  3. Click the Sample Editor tab to load the sample you want for that instrument.

  4. Click the Tracker tab, use the arrow keys to position the cursor box over the first event entry space for Instrument 1 and select the note desired from the QWERTY or MIDI keyboard as described above. Remember, any note can be deleted simply by selecting it again and pressing the computer keyboard's Delete key.

  5. Repeat this process for each beat until you have the pattern and instrumentation desired. You can play your pattern at any time, a feature that greatly speeds up the composition process.

Event Details

We have already seen that the event entry line has four fields, shown as columns of numbers, indicating the pitch chosen for the sample playback, the instrument number, the volume and the effects field. The effects field combines the effect command and parameter value into one three-digit entry. Only the pitch indicator follows the traditional pitch/octave notation; all other values are represented by decimal or hex numbering (you can select the representation you prefer).

The effects command not only adds typical effects such as vibrato, tremolo, LFO and filtering, it also provides signals to start the subsequent pattern, jump to a new position in the event list, and even jump to a new position and loop from that point for a specified time. It also provides a fine-tuning parameter for more accurate intonation of a sample at a particular pitch level.

The highlighted line in Figure 2 shows a typical tracker event entry: a bass instrument with a pitch of C6 and the defaults for volume and effects. The entry is located on the first beat of a four-beat pattern.

Figure 2. A Single Bass Note in a Four-Beat Pattern

Figure 3 shows the procedure carried out to create a C major scale, rising over a period of 16 beats, from C6 to C7 (the highlight line is mid-scale at F6). In Figures 1 and 2, the tempo has been set to 100BPM (beats per minute), and only two channels are represented, with nothing in channel two yet.

Figure 3. A Scale Played by the Bass Instrument

Note that SoundTracker provides a Tempo control as well as a BPM setting. This control is perhaps best thought of as a kind of “throttle” over the BPM setting. A Tempo of one is the fastest, and all higher numbers gradually slow the speed of the pattern playback. The default Tempo of six matches the BPM to the speed of a metronome with the same BPM setting. Note also that Tempo and BPM are global, so changing their settings will affect the speed of all patterns in your song.

The pattern length and number of channels can be varied at will in the global section. Changing the pattern length or the number of channels in the global section immediately updates both the global and tabbed sections.

Figure 4 shows a more complex pattern from a completed song. The screenshot was taken while looping pattern five, so you can see the activity of the individual instruments in the oscilloscopes at the upper right. The pattern is set to 16 beats (4/4 time) with events added for bass guitar, bass drum, snare, hi-hat, cymbal and guitar.

Figure 4. A More Complex Pattern