Legalism -- and Jesus says idolatrous worship -- is deriving acts of worship to be performed for other people. This is not burning animals but is ceremonial legalism which is idolatry -- the worship of self-selected talent who have signed onto "The Good Ship Sacrifice" as master while the honest evangelist does the real work. Legalistic or vain or idolatrous worship was defined by Jesus as coming out of their own empty heads:
He answered and said unto them, Well hath Esaias prophesied of you hypocrites, as it is written, This people honoureth me with their lips, but their heart is far from me. Mark 7:6
Howbeit in vain do they worship me, teaching for doctrines the commandments of men. Mark 7:7
Vain or empty worship is depraved or idolatrous worship:
Maten (g3155) mat'-ane; accus. of a der. of the base of 3145 (through the idea of tentative manipulation, i.e. unsuccessful search, or else of punishment); folly, i.e. (adv.) to no purpose: - in vain.
In Isaiah 29 God warns of people who could not or would not read or sing the words in the book True sacrifice or praise is returning God's Words back to Him because we simply are not literate enough to approach Him with the sacrifice which we have concocted out of blind minds.
Wherefore the Lord said, Forasmuch as this people draw near me with their mouth, and with their lips do honour me, but have removed their heart far from me, and their fear toward me is taught by the precept of men: Isaiah 29:13
QUOTED FROM ISAIAH:
Isaiah did not define a true fast or worship as something which you do but something you do not do:
If thou turn away thy foot from the sabbath, from doing thy pleasure on my holy day; and call the sabbath a delight, the holy of the Lord, honourable; and shalt honour him, not doing thine own ways, nor finding thine own pleasure, nor speaking thine own words: Isaiah 58:13
Thus saith the Lord of hosts, Hearken not unto the words of the prophets that prophesy unto you; they make you vain: they speak a vision of their own heart, and not out of the mouth of the Lord. Jeremiah 23:16
These false prophets, and increasingly prophetesses, will violently attack Biblical worshipers by accusing them of being legalistic because they refuse to have their mind manipulated by "talented" song and sermon. However, as prophesied, this is turning the truth upside down: the legalistics are the performance worshipers:
These are murmurers, complainers, walking after their own lusts; and their mouth speaketh great swelling words, having mens persons in admiration because of advantage. Jude 1:16
THE VERSION FROM EZEKIEL clearly identifies all performance music as belonging to the sectarian HYPOCRITES.
Also, thou son of man, the children of thy people still are talking against thee by the walls and in the doors of the houses, and speak one to another, every one to his brother, saying, Come, I pray you, and hear what is the word that cometh forth from the Lord. Eze 33:30
And they come unto thee as the people cometh,
........ and they sit before thee as my people,
........ and they hear thy words,
........ but they will not do them:
for with their mouth they shew much love,
........ (Lord, Lord as amorousness - inordinate love),
........ but their heart goeth after their covetousness. Eze 33:31
Indeed, to them you are nothing more than one who sings love songs (minstrel as a prostitute) with a beautiful voice and plays (make melody on) an instrument well,
for they hear your words but do not put them into practice. Eze 33:32NIV
When all this comes true--and it surely will--then they will know that a prophet has been among them." Eze 33:33
From: Agab (h5689) aw-gab'; a prim. root; to breathe after, i. e. to love (sensually): - dote, lover.
The Spirit of Christ (1 Peter 1:11, Rev 19:10) speaking through pointed to the Hypocrites who were a SECTARIAN group of religious performers said, in effect: Musical performance is hypocritical (by definition) and is therefore JUST NOTHING at all.
Because their performance effort is divisive their actions and Jude define them as the true sectarians.
Hupokrinô reply, make answer
2. expound, interpret, explain [outlawed by Peter as private interpretation] II. Att., speak in dialogue, hence play a part on the stage, be an actor, kômôidian, of orators and rhetoricians, represent dramatically, use histrionic arts, exaggerate, deliver a speech, declaim, of orators and rhetoricians, represent dramatically
rhêtor-ikos , ê, on, oratorical, hê rhêtorikê (sc. technê). These are the craftsmen lumped with the singers, musicians and "grinder" doing merchandise in the house of prayer. Rev. 18:22
hupo-kritikos , ê, on, belonging to hupokrisis 2. suited for speaking or delivery, lexis -kôtatê ib. 1413b9, cf. Demetr.Eloc.193: hê -kê (sc. technê) the art of delivery
One of the roles was as canto I. Neutr., to produce melodious sounds (by the voice or an instrument), to sound, sing, play (class. in prose and poetry; to sing and play while the actor accompanies the song with gestures or dancing, C. Transf., of instruments, to sound, resound:
And the voice of harpers, and musicians, and of pipers, and trumpeters, shall be heard no more at all in thee; and no craftsman [TECHNE], of whatsoever craft he be, shall be found any more in thee; and the sound of a millstone shall be heard no more at all in thee; Rev 18:22