Explanation of Musical Atlas: Project 2 | Listening to the Musical Atlas

MUSICAL ATLAS: PROJECT 1
(Plain Melody & Composition 1)

by Joanna de la Cruz (RU '98)

INTRODUCTION

DNA can be represented in a variety of ways, which can provide different visual perspectives of molecular structure.

DNA can also be aurally represented when a correspondence is created between the bases and musical notes, as seen in Dr. David Deamer's earlier work DNA Suite (1983).

This Musical Atlas presents an aural representation of the B-DNA molecules without mismatches, drugs, or modifiers that were contained in the NDB as of July 25, 1996.

This atlas follows a newly created pattern. For each structure, there is a "Plain Melody," which follows a simple algorithm to highlight the structure's sequence, and a "Composition," which follows a more complicated algorithm that features the base pairing of the structure.

These algorithms contain rules for determining the meter and rhythm for each piece.

In each case, the notes are assigned to each base as follows:

These are found within the range a to g¹.

Each base of the asymmetric strand is given one note. The strand is read 5' to 3'.

Thymine was assigned to E so that the four bases would fall into an a minor seventh chord.

PLAIN MELODY

In each melody, each base in the sequence is played for one beat. If there are four adenines in a row, the note A will be played four (separated) times. If there is only one cytosine, it will be played for one beat, etc. In these melodies, the sequence for each structure is played once. The purpose of this Melody is to provide the listener with a 'feel' for the nucleotide without accompaniment.

The Plain Melody for BDF062, Strand A (C G C T G G)

COMPOSITION 1

For each composition, there are four measures in which every quarter note gets one beat.

The number of beats per measure is based upon the length of the nucleotide; the number of beats per measure is half the number of bases per strand. For example, if the nucleotide is 12 base pairs long, then the number of beats per measure will be 6 (time signature = 6/4).

The sequences used here all had an even number of base pairs. However, if a sequence contained an odd number of bases, the number of beats per measure will be half that amount minus the remainder. For example, a 13 base pair piece would get 6 beats per measure.

Each base in the asymmetrical strand is an eighth note (as opposed to the quarter note used in the Plain Melody; an eighth note is half the length of a quarter note).

The compositions consist of two lines:

Melodic Line

The melodic line is the melody derived directly from the sequence of the molecules. If the asymmetric strand is self-complementary, the DNA molecule will have only one melody. If the strand(s) in the asymmetrical unit is(are) not self-complementary, both the asymmetrical strand and its symmetry related strand each have a separate melody.

In this algorithm, there are four measures to each melody. The melodic line consists the sequence being repeated of the asymmetrical sequence being repeated four times.

If a base repeats itself in a sequence, the repeated note is tied (ie., if two adenines are in a row, then an A will play for a full quarter note.) For example, the sequence C G C A A A T T T G C G (BDL038) will have an A playing for one and a half beats (a dotted eighth note), and a E for one and a half beats. The cytosines and guanines are all eight notes.

Bass Line

The first measure is a full measure rest for the bass line while the full sequence is played on the melodic line.

The second measure begins with the complimentary strand. This strand is read 3' to 5' (essentially, it base pairs with the melody). For example, when a C is playing in the melodic line, a G is played in the bass line; when an A plays in one, an E will play in the other, etc. The bass line should be smooth as the line will allow and should follow fundamental rules of counterpoint. Both the melodic and the bass lines have the same rhythmic structure in this measure.

The third measure slightly expands upon the base pairing concept of the second measure. Using notes from the a minor scale, the base pairing note in the bass line is followed by specifically assigned notes to create counterpoint while the melody is being held.

The base pair will play at the same time as the base in the asymmetrical strand but will only play for half the amount of time given in the second measure. It will then be followed by the new note assigned by the algorithm having the same time length as the base pair preceding it. For example, using the same sequence as above, C G C A A A T T T G C G, cytosine's note is a C. When the C plays for half a beat (eighth note) a G plays in the bass line for one quarter of a beat (sixteenth note) followed by an F which is also played for one quarter of a beat (sixteenth note). For the dotted quarter note A, the bass line will have an E playing for half that time followed by a D played for the same amount of time.

The fourth measure ends in a somewhat static chord progression. Each base in the melodic line is accompanied by its corresponding chord in the bass line. To create a stable chord, it was decided that these chords should be a fifth down from the base note, and should be in the same key signature (a minor).The chords assigned by the algorithm will play simultaneously with the corresponding bases in the top line. Chord inversions are acceptable as long as the line is kept as smooth as possible.

The Composition for BDL038

Acknowledgements
Thanks to Jason Young for providing technical assistance.

back to top