The usage of a dowsing pendulum for testing human prana is only an option. In my experience dowsers have always reflected my inner most wishes and I would therefore recommend an impartial application for testing anything.
A seasoned practitioner of Saraswati Veena (acoustic and made of Jack wood) has the capacity to feel the energies of a Veena merely by playing on the instrument. A Veena yogi who has developed clairvoyance through Veena playing is able to scan the energy of a Veena even without touching the instrument.
Our elders and Gurus have time and again cautioned us to never let a Veena be idle at home and to maintain Veena clear of dust/dirt and with good 'melam' (alignment of frets). It is extremely harmful to keep a Saraswati Veena with unaligned frets (bad 'melam') that result in discordant notes ( apaswaram in swarasthanas). These are healthy and disciplined principles to follow for a beginner on a brand new Saraswati Veena in order to invoke positive energies and vibes in one of the most potent and divine instruments. By following these principles the beginner prevents bad energies from entering the instrument.
What happens when a Saraswati Veena which is not brand new and containing the prana of a practitioner is left to idle and get dirty/dusty with unaligned frets? Such a sad state of the instrument which is connected to the said practitioner directly affects his/her well being in life. It could affect health/emotional issues/ finances etc. of the pratitioner. The practitioner has created a huge responsibility for himself in extending his life force energy by creating an outside branch of himself in an occult instrument like the SARASWATI VEENA.
Veena containing human prana has to be kept clean and all frets in perfect alignment. Further the Veena should be cleansed of bad "drishti" by regular offering of lighted camphor. If not daily at least on Fridays 'kumkum' and sandal paste should be placed under the bridge which is close to the forehead of the practitioner and in the proximiity of his/her Agna Chakra. Even further fresh or dry fruits and whatever naivedhyam is offered to God has to be offered to the Saraswathi Veena in order to nurture the extended life of the practitioner. The other side of the coin-how else is Veena used as a carrier of energies?