You should pick up one of the instruments that guru sahib blessed us with, whether it be the rabab that guru nanak dev ji got specially made by bhai firanda and sang with while travelling the world, or the saranda which guru arjun dev ji created himself and did kirtan with, or the jori, not tabla (jori is much more different, tabla is a newer invention), which was created by bhai satta bhai balwand in guru arjun dev jis darbar, or the sarangi which was brought in by guru hargobind ji, or the taus and dilruba which were created by guru gobind singh ji. all the guru's did kirtan with these instruments.
for the topic that where does it say that we cannot play the vaaja, well there thousands of instruments in india why were they not chosen, and why did the gurus go through the trouble of making special instruments to do kirtan with.
if an english doctor could come to look at guru gobind singh ji at nanded when he was stabbed, why could a piano or something not also arrive. guru nanak dev ji travelled to rome, why did he not choose a piano or violin to play. The gurus had the choices but they chose and made these instruments.
and raag kirtan is NOT HARD. when you laugh or cry, that is raag. raag is an emotion, something you cant describe.
gurbani is written in raag as it should be sung conveying that emotion. that is how the gurus wanted us to feel and connect. or else the gurus could have done it any other way. raag kirtan is so easy
and lastly it is hukam. if it says asa mahalla 1, then who says you can sing it any other way? right?
bhul chuk lai khima, sangat bakhshan jog hai, bakhsh laina, daas de bas 2 cent ne aa
thanks