A few years back, while in conversation with a man who is well-versed in 'tantrik yoga', I was advised to wear an abdomen belt while playing the veena. He said it was necessary to always keep in mind my posture even while engrossed in the melody of the Veena. Practitioners tend to stoop (especially when they are tall and broad-shouldered) while they are absorbed in playing the Veena.
That is precisely the reason why one should start learning to play the veena at a very young age, when the child's head barely reaches the veena dandi. The child's spine is naturally erect, owing to the small trunk of the child. The spinal chord is straight as the the child reaches upwards to run the left hand over the veena frets. By starting from a very young age, the practitioner gains enormous pranic-strength, as the naturally erect spine facilitates the smooth, upward flow of the life-force energy arising from the Mooladhara Chakra.
Looking at Teacher (Smt. Kalpagam Swaminathan), I was able to understand her capacity to play so effortlessly at the age of 87! For somebody who needs to be assisted while walking, she is remarkably at ease as her hands work out the most complicated prayogas on veena. Being of average build, her height seems to have lessened further (due to ageing), forming a natural alignment of her chin and the veena-dandi. Her build, almost like that of a child of 10/12 years, is ideally suited for veena-playing, as her erect spine allows the smooth, upward flow of Kundalini. Physical strength is no match for life-force energy (kundalini shakthi) which can be activated only through erect posture of the upper trunk of the practitioner.
As a matter of interest, anybody could practically witness /experience the difference between playing the veena by a)hunching over the instrument and by b) sitting absolutely erect (without even the slightest bend in the upper trunk of the body). The player would feel tired and insipid while playing in the former position, whereas he/she is instantly rejuvenated when the shoulders are pushed back and the entire upper portion of the trunk is stiff and erect as per the latter position.
One need not worry about posture while playing the modern, distorted versions of Veena that are available in the market. While playing the Saraswathi Veena, every note produced has to be nurtured through Kundalini Yoga which is possible only through correct posture.