The word phrt, pereth, means to divide; so some explain it, and derive it from the clusters which remain after the vintage, because there are not then thick grapes, but a cluster here and there, and a great distance between: hence they think that the participle hphvrtym, epurethim, is to be taken here metaphorically as meaning to divide by marks, as music has its various notes; for except there be a distinct variety in singing, the sound would be confused, and would produce no pleasing effect. Who sing then with the harps and have invented for themselves, after the example of David, musical instruments. The Prophet still continues his discourse, and shows that these men lived sumptuously; as though they did not belong to the common class, they delighted themselves, against God's will, not only in the common mode of living, but even sought new pleasures, as if they were continually at marriage feasts, or celebrating birthdays. As then they had no season for mourning, they pursued their own indulgences; and this is what the Prophet now reprehends. If then any one thinks that music is in these words condemned, he is much deceived, as it appears from the context. Indeed, the Prophet never dealt so rigidly with that people, but he ever kept to this point -- that they were extremely torpid, nay, destitute of common sense, who perceived not that God showed himself angry with them, in order that they might flee immediately to the standard of repentance and humbly deprecate, with mourning, the wrath of God, as they ought to have done. It was therefore meet ever to set before them Gods wrath, which ought to have humbled the Jews and the Israelites, inasmuch as they ever obstinately set up against God their own indifference. In saying that after the example of David they invented for themselves musical instruments, he no doubt greatly aggravated their sin by this comparison: for it is not likely that they had abused this pretext, as hypocrites do, who are wont to boast of the examples of the saints, when they seek to disguise their own vices, -- "What!" some will say, "Did not David use musical instruments?" Others will say, "Had not Solomon very splendid palaces?" And some will add, "Had not Abraham a company of servants in his house?" So every one lays hold on what may avail for an excuse: and thus the examples of the saints are absurdly referred to by many. But it seems not probable that this was done by those whom Amos now addresses: but, on the contrary, he appears sharply to reprove them for provoking God's wrath by self indulgence, and for manifesting their perverseness, while David employed musical instruments in the exercises of religion, to raise up his mind to God. No doubt, David, when in a peaceful state, after having been delivered from all dangers, could also amuse himself: but he applied musical instruments to another purpose -- to sound forth the praises of God in the temple, that thereby he and other godly persons might together elevate their thoughts to a religious devotion. While David then, even in a state of peace and prosperity, did not allow his mind to become sunk in vain self-indulgences, these men, when God appeared angry, when he spread terror by so many tokens of his vengeance, yet dared contumaciously to follow their own ways, so that they left off nothing of their usual pomp and of their accustomed pleasures. We now see the design of the comparison which the Prophet makes: He aggravates, I have no doubt, their sin, because they regarded not the example of David, but transferred musical instruments to serve the purpose of gross and beastly indulgences, and thus they did when God was opposed to them, when he had begun to terrify them by his vengeance. Let us proceed --

That chant to the voice of the lyre - Accompanying "the voice of the lyre" with the human voice; giving vocal expression and utterance to what the instrumental music spoke without words. The word, which Amos alone uses in this one place, describes probably a hurried flow of unmeaning, unconsidered words, in which the rhythm of words and music was everything, the sense, nothing; much like most glees.
The English margin "quaver" has also some foundation in the root, but does not suit the idiom so well, which expresses that the act was something done "to the voice of the lyre," accompanying the music, not altering the music itself. In fact, they would go together. An artificial, effeminate music which should relax the soul, frittering the melody, and displacing the power and majesty of divine harmony by tricks of art, and giddy, thoughtless, heartless, soulless versifying would be meet company. Debased music is a mark of a nation's decay, and promotes it. The Hebrew music seems to have been very simple; and singing appears to have been reserved almost exclusively for solemn occasions, the temple-service, or the greeting of victory 1-Samuel 18:7. "Singing men and singing women" were part of the state of David and Solomon 2-Samuel 19:35; Ecclesiastes 2:8. Else the music at the feasts of the rich appears rather to be mentioned with blame Isaiah 5:12; Isaiah 24:9. Songs they had Proverbs 25:20; but the songs, for which the Hebrew exiles were celebrated, and which their Babylonian masters required them to sing, "the songs of Zion" Psalm 137:3-4, were the hymns of the temple, "the Lord's song."
And invent to themselves instruments of music - The same pains, which David employed on music to the honor of God, they employed on their light, enervating unmeaningful music, and, if they were in earnest enough, justified their inventions by the example of David. Much as people have justified our degraded, sensualizing, immodest dancing, by the religious dancing of Holy Scripture! The word can mean no other than devised. David then did "devise" and "invent" instruments of music for the service of God. He introduced into the temple-service the use of the stringed instruments, the "kinnor," (the "lyre") and the "nebel" (the "harp") in addition to the cymbals. Whence these, in contrast with the trumpets, are called "the instruments of David" (2-Chronicles 29:26, compare 2-Chronicles 29:25, and 1-Chronicles 15:16, 1-Chronicles 15:19-21, 1-Chronicles 15:24). Probably, in adapting them to the temple-service, he, in some way, improved the existing instrument; having been, in early youth, remarkable for his skill upon the harp 1-Samuel 16:16, 1-Samuel 16:18, 1-Samuel 16:23. As he elevated the character and powers of the, perhaps rude, instrument which he found, and suited it to the service of God, so these people refined it doubtless, as they thought, and suited it for the service of luxury and sensuality. But what harm, they thought, in amending the music of their day, since so did David?

And invent to themselves instruments of music, like David - See the note on 1-Chronicles 23:5; and see especially the note on 2-Chronicles 29:25 (note). I believe that David was not authorized by the Lord to introduce that multitude of musical instruments into the Divine worship of which we read, and I am satisfied that his conduct in this respect is most solemnly reprehended by this prophet; and I farther believe that the use of such instruments of music, in the Christian Church, is without the sanction and against the will of God; that they are subversive of the spirit of true devotion, and that they are sinful. If there was a wo to them who invented instruments of music, as did David under the law, is there no wo, no curse to them who invent them, and introduce them into the worship of God in the Christian Church? I am an old man, and an old minister; and I here declare that I never knew them productive of any good in the worship of God; and have had reason to believe that they were productive of much evil. Music, as a science, I esteem and admire: but instruments of music in the house of God I abominate and abhor. This is the abuse of music; and here I register my protest against all such corruptions in the worship of the Author of Christianity. The late venerable and most eminent divine, the Revelation John Wesley, who was a lover of music, and an elegant poet, when asked his opinion of instruments of music being introduced into the chapels of the Methodists said, in his terse and powerful manner, "I have no objection to instruments of music in our chapels, provided they are neither Heard nor Seen." I say the same, though I think the expense of purchase had better be spared.
The word הפרטים happoretim, which we render chant, and the margin quaver, signifies to dance, to skip, etc. In the sight of such a text, fiddlers, drummers, waltzers, etc., may well tremble, who perform to excite detestable passions.

That chant to the sound of the viol, [and] invent to themselves instruments of musick, like (e) David;
(e) As he caused different types of instruments to be made to serve God's glory, so these did strive to invent as many to serve their unrestrained affections and lusts.

That chant to the sound of the viol,.... Or psaltery; an instrument of twelve cords, and that gave twelve sounds, as Josephus (x) says, being stricken with the fingers; and to these sounds these men chanted or quivered, made like sounds with their voice, which they raised higher or lower, according to the sound of the instrument: they "particularized", as the word signifies (y); or observed the divisions and distinctions of notes and sounds, by the modulation of their voice:
and invent to themselves instruments of music, like David: not content with old ones, such as were used in former times, they invented new instruments and new tunes, and new songs to sing to them; as David made songs and invented several instruments of music to sing them upon and to, in religious worship, and for the praise and glory of God; so these men invented new ones to indulge their carnal mirth and jollity, in which they thought themselves to be justified by the example of David.
(x) Antiqu. l. 7. c. 19. sect. 3. (y) "particularizantes", Montanus; "qui particularia habent cantica", Pagninus; "qui particulatim canunt", Vatablus, Mercerus; "variis modulationibus concinunt", Tigurine version.

chant--literally, "mark distinct sounds and tones."
viol--the lyre, or lute.
invent . . . instruments . . . like David--They fancy they equal David in musical skill (1-Chronicles 23:5; Nehemiah 12:36). They defend their luxurious passion for music by his example: forgetting that he pursued this study when at peace and free from danger, and that for the praise of God; but they pursue for their own self-gratification, and that when God is angry and ruin is imminent.

That chant - That in a time of deep mourning entertain themselves with songs, and musical instruments.