Answer to Question 1
The original hand-held plectrum (like a guitar pick) was replaced with false fingernails of various materials (bone, shell, etc.) so that each finger could independently pluck the strings of the pipa. This permitted varied and virtuosic (technically advanced) playing on the instrument.
Many different strokes can be used including today's standard strokes described in Worlds of Music. The pipa can sound multiple strings, e.g., creating a melody played on the highest-pitched string that is accompanied by strums across the other lower strings.
The use of harmonics (lightly touching the strings at certain places to create different pitches) or pressing a stopped string sideways to create a rise in pitch or pitch-bend
Answer to Question 2
In 1950 Chinese musicologists recorded Abing playing three solos on the pipa (a four-stringed pear-shaped lute) and three solos on the erhu (a two-stringed fiddle). The music was apparently from his street repertory.
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Western musical instruments.