I don´t think Bhakti is necessary. It can help you get into the "mood" so that it is easier to concentrate. And chanting helps you because of it´s vibration.
But the important path for an advaitin is meditation.
Maya
What is bhakti? Who is called as bhakta? What you do in meditation?
The difference is the bhava and what we call as bhakti. 'I am not different from brahman' is called as bhakti. 'Total surrender of Ego to the SELF' is also called as bhakti. Another name of Jnani is 'Brahma-NishTha'. NishThaa means shraddha or faith. So the one who has strong faith that 'I am Brahman' and abides in it or is Brahman is called as Brahmanishtha.
If you define bhakti as singing hymms of personal deity then there ar bhajans of advaita nature like that sung by Narasimh Metha, Ganga Sati, Shri Raang Avadhut Maharaj, Bhole Baba's Vedanta Chandaavali or Vedanta Geetavali is also purely advaitaic and at times ajaata vaada.
As you have said lisstening to bhajans of Rama and Krishna are also helpful to prepare mind for meditation. Meditation is either Self Enquiry or OM. Most advaitins meditate on OM.
Bhakti, shraddha, samarpaNa, etc are all needed, but the way we define from dvaita POV is not the only way. Advaita does accept someone is higher than you i.e. Brahman / Atman. The very verse that is very famous and is said to sum up teachings of Adi Shankara is Brahma Satya, Jagad Mithya, Jivo Brahma Na Aparah.
It says Jiva and Brahma are not different. In this statement the duality is accepted in vachyaartha i.e. there is Jiva and Brahman which are separate when one is under maya i.e. one is ignorant (ajnaani). But the laxyaartha is that Jiva and Brahman are same. So advaita asks one to rise above dvaita. Dvaita is not negated from day one. The question is - why this world is said to be an illusion to ajnaani and how will this concept help one to progress? An Advaitin should think on it. Meditate on OM. The one who meditates on any mantra, be it OM or Om Shri Rama Chandraya Namah or Om Namah Shivaya, the status of mind is reflected. The reason why this world is said to be an illusion can be understood only to sincere meditators.
Even the mahavakya I am That, becomes non dual (for seeker) only if one realizes that I am That. That is brahman but this 'I' does not know that 'I' is that Brahman. The word AM is important as it makes the statement non-dual. Replace it with AM NOT -
I AM NOT That
So the laxyaartha is to realize that 'I' is Brahman and not Ego, sarira, jiva, buddhi, sukshma sarira, etc. To know the real nature of 'I' one has to enquire 'Who Am I', and dive deep within, into the source of thoughts, breath, OM, into the source where mind and intellect gets power and becomes active. This is very technical stuff and difficult to understand. Only a Guru can make you understand and God can give you experience of Who you are.
Bhakti is the base, necessary foundation. Without bhakti, one cannot be a Jnani. Even though one may not practice saakaara bhakti, he / she must have done it in past life / lives. As one is always in dvaita. Bhakti is stepping stone. Though through saakaara bhakti, one can have divine vision of God, one according to prakruti, can shift to advaita after the mind is stabilized. Advaita is not for everybody, but anyone can practice saakaara bhakti, specially it suits emotional temperaments says Swami Sivananda of Divine Life Society in Glory of Bhagavad Gita.
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