New Document

Bang

Dodecaphonic piano solo, banging chords up to a final tonal melodic+harmonic cadence. There are no harmony constraints, except at the final close; any group of notes may be sounded together.
The instruction:
perl driver.pl rnd_1234 irrhy_4
will produce a score bang1234 and a playable midi file bang1234.mid. In more detail, driver executes:
 
perl  preloo.pl  @ARGV  
type  PARM.txt  
perl  loo.pl  >  resul.txt    
perl  bang.pl  
copy  hdrbang.txt+lh.txt+rh.txt  $score    
midi  $score

subprograms

preloo.pl
- parses the parameter list
  rnd_1234 irrhy_4
  – as supplied to driver.pl – and makes a file PARM.txt to be used later.
- the parameters are interpreted as follows:
  - initialize the random number generator with 1234
  - irrhy (irregularity in rhythm) is a number between 0 and 6, to scale the probability of departing from the standard rhytmic pattern. The default value is 5. The higher the value, the more irregular will the rhythm be.
- the series is constructed using the random number generator. The series and all the distinct transposed linear aspects (uaually 48, but possibly fewer) are written on PARM.txt
- writes PARM.txt
loo.pl
Creates various cyclic joins from the series, and assigns grades to them. This, in addition to other stuff, gets written on the intermediate file resul.txt
- reads PARM.txt
- writes resul.txt
bang.pl

Creates the actual score, from the best cyclic join made by loo.pl. The score consists of 3 parts:

a number of regular chords, blocked in the left hand, blocked and also spread in the right
The piece is in ternary rhythm, with the left hand chords repeated 3 times each, and the right hand pattern:

mid blocked chord,
low blocked chord,
high spread chord (i.e. a melodic pattern based on the chord).
With small probability, the pattern is changed for one measure (a single chord) at a time. Both hands may play arpeggios over the whole piano range (i.e. my midi piano range), or the right hand may spread 2 or 3 beats, instead of the standard one.
The chords are taken from the cyclic join, first two notes at the time, then three, up to five. The 4 and 5 notes chord may be hard to play; actually, since my chip has only 9 channels, 5-notes chords contain five distinct sounds in the right hand, but only four in the left. I check at least that the range for each hand is less than 15 semitones, and hope that certain pairs can be played with one finger.
As an example, from

A♭  B  C  A  B♭  E♭  D  E  C#  F  F#   G ...
one may generate 4-note chords:
A♭  B  C  A
B  C  A  B♭
E♭  D  E  C# ...
There may be overlap in the chords, and, of course, no note may be skipped – that would spoil dodecaphony.

a segment with more rhythmic variety,before the final close ( prefinal )
The same changes in rhythm as above, but at higher probabilities. It contains non-overlapping chords of 4,3,3,4,5 notes, 19 notes in total.

the final close, a melodic and harmonic cadence made of 3 blocked chords in both hands
This cadence is located in the cyclic join by the routine findcad ( it appears somewhere at random, and may not exist at all – in this case the program increases the random seed, and restarts at preloo.pl ) It is played first as a regular measure, than as a two-hands arpeggio, finally as a melodic cadence above supporting tonal chords.
This is the end of the piece.

reads PARM.txt
reads gratra.txt, which is a huge file with data about all the possible melodic/harmonic cadences. The file is so large, you may notice the program "halting", with no output for a few seconds. It usually keeps printing, just to show it is alive.
writes lh.txt and rh.txt, separate score for the 2 hands, which are then combined into one score.

Cadences

A cadence is a harmonization of one of the melodic cadences:

LA SI DO
RE SI DO
SI RE DO
SI DO
RE DO

(all of the above in minor or Major scales)

MI RE DO – Major scale only
MI♭ RE DO – minor scale only

SI / RE – DO should be harmonized as V / V7 / VII7♭, / I / i , with any fitting triad for LA / MI / MI♭. The fuller the harmony, the better the cadence. Components may be missing, e.g. I / i may be reduced to tonic only, V7 played without third or fifth – and the grade of the cadence reduced accordingly.
Such cadences may appear by chance in the piece – they are not part of the design. In fact, the common melodic cadences DO SI DO and DO RE DO may also be there, although a single melodic dodecaphonic line should not contain them. In any case, I ignore DO SI DO and DO RE DO.