Archangels are the second-lowest choir of angels, above only regular angels. Above them are principalities, powers, virtues, dominions, thrones, cherubim & seraphim.

IDK whether the population of the choirs is even or pyramidal, but either way suggests many, many more than 7 archangels.

As for the vibrational attunement, I've speculated idly that conforming to the commandments of God and the importance of prayer, mediation, and charitable thoughts and actions are all ways to put one's spiritual self on the same frequency, as it were, with God, thus enabling the spirit to be with God once it is free of its material chrysalis.

But however plausible the concept of the method, I strongly doubt the efficacy of so superficial a method. Or that such vastly more powerful beings could be invoked by anything within human capacity.