1. To write a motive based on the given melodic line, you would identify the most distinctive and memorable part of the melody and use it as the basis for a short, recurring musical phrase. This could involve selecting a particular rhythmic pattern or melodic interval from the original melody and repeating it in different contexts throughout the composition.
2. A melodic motive and chord progression work together to create a sense of harmonic motion and tension and release in a musical composition. The harmonic structure of a piece can influence the melodic choices made by the composer, and conversely, the melodic motifs and themes can shape the harmonic progression of the piece.
3. The chord progression shown might be described as a basic I-IV-V progression in the key of G major, where the I chord (G) is followed by the IV chord (C) and the V chord (D7). This progression is commonly used in many styles of music, including rock, blues, and country, and provides a simple and effective harmonic foundation for many different melodies and songs.
4. To make variation in music, you can experiment with changing different elements of the composition, such as the melody, rhythm, harmony, or instrumentation. Examples of variation in different musical styles might include adding new instrumental parts, changing the tempo or meter of a piece, or altering the chord progression or harmonic structure.
For example, in jazz music, musicians often use improvisation to create variations on a basic melody or chord progression, incorporating different scales, modes, and rhythmic patterns to create new and interesting variations on the original theme.
5. The definition of a "good" composition can vary depending on a wide range of factors, including cultural context, personal taste, and historical perspective. Some people might value technical virtuosity and complex harmonic structures, while others might prioritize emotional expression and simplicity of form. Ultimately, the quality of a musical composition is subjective and can be evaluated in many different ways depending on the individual listener's perspective.