The flute is a versatile instrument that can produce a sweet sound across various scales. However, the sweetness of the sound is subjective and can vary depending on the player's technique, embouchure, and personal preference. Different scales can evoke different moods and emotions, so it ultimately comes down to individual interpretation.
That being said, the major scale is often considered one of the most pleasing and versatile scales in Western music. Its pattern of whole and half steps creates a sense of balance and consonance, which can contribute to a sweet and harmonious sound. The major scale is frequently used in melodies and compositions across different musical genres.
It's important to note that a skilled flutist can produce a beautiful and sweet sound on any scale, as the quality of the sound primarily depends on their technique, breath control, and musical expression.