Jazz improvisation is a complex art form that requires years of dedicated practice to master. While there are many ways to approach learning improvisation, playing by ear is one of the most effective methods for developing a deep understanding of the music.
According to a study by the Berklee College of Music, playing by ear is a critical skill for jazz musicians. The study found that students who developed their ear training skills early on in their studies were better able to improvise later on.
Source: https://www.berklee.edu/bt/152/eartraining.html
Playing by ear involves listening carefully to the music and then reproducing it on your instrument without the aid of written notation. This requires a strong sense of musical memory, as well as an ability to hear and recognize harmonic and rhythmic patterns.
Source: https://www.jazzadvice.com/the-ultimate-guide-to-playing-by-ear-for-jazz-musicians/
While playing by ear is an essential component of jazz improvisation, it is not the only one. Improvisation also requires a deep understanding of harmony, melody, rhythm, and form, as well as the ability to communicate musically with other musicians in real-time.
Source: https://www.jazzadvice.com/the-4-essential-skills-for-learning-to-improvise-jazz/
Therefore, while playing by ear can certainly help you to develop your improvisation skills, it should be combined with other approaches, such as transcribing solos, studying music theory, and practicing with other musicians.
Source: https://www.musical-u.com/learn/can-you-learn-jazz-improvisation-by-playing-by-ear/
In conclusion, playing by ear is an essential component of learning jazz improvisation, as it helps to develop your ear training skills and deepen your understanding of the music. However, it should be combined with other approaches, such as transcribing solos and studying music theory, in order to fully develop your improvisation skills.