When the Allah Hoo’s tick did hit my soul,
I dusted the clothes’ of the cosmos whole.
Hold the violin quick as the chords so soon,
Are loosing my grip by quill’s burning tune.1

1.         Here it means croon, tune or croons
Literal translation of line 2:-
Are falling like tears, from quill’s burning tune.
Here Iqbal is conveying the same idea:-

“Take the harp from hand I am going to die.” (or I am loosing the grip).
Rakht; Clothes (or I am loosing the grip).
Quill=(Zakhma in Persian). A plectrum by which the strings of mandoline etc. are played.
Allah Hoo; is a hit of “Asbat”     or affirmation (of Allah) which takes a mani to Baqa-billah (to become immortal in God’s presence). In the wake of Hazrat Mujaddad Alf Sani of Sarhand (Patiala State, in India). From Nafi (negation of gods) Iqbal flies higher to Asbat direct in wake of Sheikh Ahmad Sarhandi (birth 971, death 1034).
Study Maktubat-i-Mujaddad.