Thanks to the members on this form, gyan from Guru Granth Sahib, few other Gurmukhs, reading Sri Guru Nanak Chamatkar book by Bhai Sahib Bhai Vir Singh Ji.
I have also come to realise the Gurmantra/GurShabad should be the most important.
As Lucky said "sounds start to get captivating and magnetic, and they begin to pull you in deeper"
This is also mentioned on another site.
"it is easy for the mind to get over-involved - almost OCD - in listening to inner sounds and trying to determine which is better or "right". In the process, the mind becomes like a dog incessantly chasing its tail. Instead, Charan Singh tells us to simply keep repeating and focusing on Simran. The more your attention is wholly and solely focused upon Simran, the more it will be immersed in the Sound Current - and, in the process, the subordinate sounds will fade into the background and the real, Eternal Sound will emerge into your focus, lift you up above body-consciousness and guide you within"
As it says in Guru Granth Sahib chant the Gurmantra, day and night while standing, sitting, sleeping, eating, walking, working, etc.
Gurmukh said if we can not make our mind sit without taking thoughts for 3 hours then it will be very heard to merge into naam. Therefore, must keep doing simran to make mind sit.
If we take a thought to transition from Gurmantra to Naam then we take a thought which will put us back into Maya, Therefore, make mind so still that when Naam comes it automatically pulls you within without you taking a thought.
Also to add, Gurpreet Shimla Wale in his kirtan/katha mentioned that we are to keep chanting the Gurmantra because it will eventually go into rom rom (heartbeat and cells).
I think that once Gurmantra goes into heartbeat, then one is able to listen to the Naad. It says in Guru Granth Sahib Ji "the Sound-current of the Naad vibrates in each and every heart".
If I made any mistakes, forgive me, I too am still learning on this path.
Man tan antari Hari Hari Mant. Nanak bhagtan kai ghar sadaa anand: The Mantra of God's Name, Har, Har, is deep Within my mind and body. O Nanak, eternal bliss fills the home of God's devotees (sggs 802).
Raam Naam Mant hirdai daivai Nanak milan subhaaye: The Mantra of the Raam Naam is enshrined Within the heart, O Nanak, and we merge with Him so easily (sggs 444).