At the hadlaka for Lag B'Omer everyone was dancing. After a bit a man whose face just shown - his countenance glowed appeared in their midst. No one knew who he was but he was b'simcha as he took the hand of the shul's gabbai and pulled him in to dance. As they swung around and around this same man reached out and took the hand of the holy Ari z"l; together the three of them danced and danced. The people were stunned - why were they dancing with the gabbai? the gabbai.
The following morning they approached the holy Ari z"l. Did he not realize, they began respectfully, that dancing with the gabbai was beneath him? and further who was that man who instigated it. The Ari z"l responded: if R' Shimon Bar Yochai danced with the gabbai himself, then surely the Ari z"l could also dance with him.
The people were stunned; that's who it had been? it actually was R' Shimon Bar Yochai? why his faced had just shone, almost otherworldly - the kedusha was supreme. Then the Ari z"l gently told them that they just didn't realize who was a tzaddik nistar and they should treat the gabbai with utmost respect. For he was.
It was after this hadlaka that R' Azkiri composed the beautiful zemer 'Yedid Nefesh'.
According to the following http://www.ascent.org.il/Stories/Stories/5768/547-37.html , that gabbai was indeed R' Azkiri.
This was told over by Yosef Karduner - and the many mistakes which must exist in my retelling are 100% my fault - as I didn't take notes when he spoke.
Beloved of the soul, Compassionate Father, ידיד נפש אב הרחמן
draw Your servant to Your Will; משוך עבדך אל רצונך
then Your servant will hurry like a hart ירוץ עבדך כמו איל
to bow before Your majesty; ישתחוה אל מול הדרך
to him Your friendship will be sweeter יערב לו ידידותיך
than the dripping of the honeycomb and any taste. מנפת צוף וכל טעם
Majestic, Beautiful, Radiance of the universe, הדור נאה זיו העולם
my soul pines for your love. נפשי חולת אהבתך
Please, O G-d, heal her now אנא קל נא רפא נא לה
by showing her the pleasantness of Your radiance; בהראות לה נעם זיוך
then she will be strengthened and healed, אז תתחזק ותתרפא
and eternal gladness will be hers. והיתה לה שמחת עולם
Enduring One, may Your mercy be aroused ותיק יהמו נא רחמיך
and please take pity on the son of Your beloved, וחוסה נא על בן אהובך
because it is so very long that I have yearned intensely כי זה כמה נכסף נכספתי
to see speedily to splendour of Your strength; לראת מהרה בתפארת עזך
only these my heart desired, אלה חמדה לבי
so please take pity and do not conceal Yourself וחוסה נא ואל תתעלם
Please, my Beloved, reveal Yourself and spread upon me הגלה נא ופרש חביבי עלי
the shelter of Your peace; את סכת שלומך
illuminate the Earth with Your glory, תאיר ארץ מכבודך
that we may rejoice and be glad with You; נגילה ונשמחה בך
hasten, show love, for the time has come, מהר אהוב כי בא מועד
and show us grace as in days of old. וחננו כימי עולם