This is not to say that all duets fit into these 2 categories or that any given duet may not change from being equal to unequal (or vice versa) during the course of the piece. These 2 types, however, give a basic idea and can serve as a point of departure to conceptualize the process of composing a duet.
One easy way to start composing duets is by considering the "treble-ground" duets written for lutes during the late Renaissance. These pieces, typical of the "unequal" duet described above, have been collected in an edition by the excellent lutenist-and former teacher of mine-Nigel North in his 3-volume collection, Tablature for Two Lutes (Stainer & Bell: London, 1983). One lute plays a simple chord progression repeated several times (the ground), while the other lute plays a single-line melody and several sets of variations on it (the treble).
Here is an example taken from a set of variations I composed for flute and guitar based on the well-known lutenist John Dowland's song called The Frog's Galliard. The example here gives the theme along with the first variation.
Notice in this beginning section of the duet the guitar, playing a simple chord progression, has the role of accompaniment while the flute carries the melody and the moving variation passages. As you compose for other instruments, make sure you know the limitations of the instruments. In the above example, for instance, note that wind players have to breath(!) so keep in mind not to let their phrases become endless. Naturally the technical abilities of the player will always determine what is practical as professional players often are able to sneak breaths very skillfully.
When composing music for voice and guitar, except in rare instances, the voice and the words will be the inevitable focus of attention. You want to write the guitar part as a complement to the voice-setting the stage for the singer-as well as bringing out the words. The form of the words can also help you define the form of the music. Writing for a singing voice is slightly different that writing for an instrument. Singers usually look for their beginning pitch from their accompanist and they also like an accompaniment that is regular and flexible.
Here is "Where Are My Roses?" which is one of 18 miniature songs from my piece Ostraka which will premiere at the Philadelphia Fringe Festival in September 2005. I gave the guitar a brief introduction to set the movement of the piece and set up the song. Notice the lyrics ask a series of 3 questions followed by 3 answers. Consequently, I gave the piece a binary form.
As with my May and June articles in this series, I have included a suggested assignment because learning to compose is an active process. This time your assignment is to compose one short piece for guitar and one other instrument. Pick another instrument you know well such as a 2nd guitar, flute, recorder, etc. Begin with a well-know melody and compose an unequal treble-ground duet with variations.
Please feel free as always to visit my web site (http://www.davidhahnonline.com). I would be happy to hear any comments or suggestions.
Next Month- COMPOSING FOR THE GUITAR PART IV: Explorations: Extended Techniques and Electronic Music with Guitar