Imitating a Drum Circle

Ever been to the park and heard a tribe drumming in the distance?  This is a drum circle. Upon closer inspection, each drummer has a single instrument (or maybe a set of bongos). Each drummer keeps a steady beat in common and in syncopation with his or her fellow drummers.

I wondered if this could be simulated somehow?  There are of course decisions to be made - parts to this equation... How should the drummers enter? All at once or gradually?  How should a drum be chosen or selected?  And what phrase(s) should be played anyway?

Enter MIDI-Perl.  Here is the program: drum-circle

Basically it does the following:

1. Use the modules necessary to have a drummer and rhythmic phrases.

2. Define the number of drummers ($max) as a number supplied by the user (or 4 by default).

3. Define a MIDI::Drummer::Tiny instance ($d), which will drive everything.

4. Set the possible drums to use (@DRUMS).  In our case this is a group of toms, bongos, congas, cabasa, maracas, guiro, claves, and wood blocks.

5. Declare an array of phrases (@phrases), which is to be populated with code-references.

6. Define a 4 bar Music::Duration::Partition instance ($mdp), which we will use to generate rhythmic motifs for each drummer.

7. Loop from 1 to $max, appending phrases to play for each new drummer.

8. Add the phrases to the score such that they are played simultaneously.

9. Write the generated "composition" to disk, as a MIDI file named after the program "drum-circle."

10. Define the subroutine to generate our phrases!

This last part is shown here:

sub phrase {
    my ($p) = @_; # Phrase number

    # Get an unseen drum to use
    my $drum = $DRUMS[int rand @DRUMS];
    while ($seen{$drum}++) {
        $drum = $DRUMS[int rand @DRUMS];
    }

    # Create a rhythmic phrase
    my $motif = $mdp->motif;

    # Either rest or play the motif
    my $phrase = sub {
        for my $n (1 .. $d->bars + 4) {
            # If we are not up yet, then rest
            if ($n < ($p * 4)) {
                $d->rest($d->whole);
                next;
            }
            # Otherwise play the rhythmic phrase!
            for my $i (@$motif) {
                # Get a fluctuating velocity between f and fff
                my $vol = 'v' . (96 + int(rand 32));
                $d->note($i, $drum, $vol);
            }
        }
    };

    return $phrase;
}

Here the variable $p is the number 1 to $max from our loop in step #7 above.  Next, an unseen drum is selected at random.  Then a quasi-random rhythmic motif is generated by Music::Duration::Partition as defined above.  Finally an anonymous subroutine is returned, that just decides whether to play the generated motif or rest for a whole note.

This resting is crucial.  Each drummer enters after 16 bars of the previous drummer having played.  So, the second drummer enters after 4 bars, the third after 8, the fourth after 12, etc.  Having everyone play at once or at random was just not a pleasant musical evolution.  So I chose to have them enter one at a time.

Each run of this is different.  Sometimes you get a "pleasant musical evolution", but sometimes you get all toms, or just a weird clash of rhythms.  Here is one with 8 voices that is ok:

And how about another?

Ok, one more!