The Odes were developed as a conscious imitation of the short lyric poetry of Greek originals. Pindar, Sappho, Alcaeus, Archilochus and Alcmaeon are Horace's models; his genius lay in applying these older forms to the social life of Rome in the age of Augustus.
The Roman writer Petronius, writing less than a century after Horace's death, remarked on the curiosa felicitas (studied spontaneity) of the Odes (Satyricon 118). The English poet Alfred Lord Tennyson declared that the Odes provided "jewels five-words long, that on the stretched forefinger of all Time / Sparkle for ever" (The Princess, part II, l.355).
The earliest positively-dated poem in the collection is I.37 (an ode on the defeat of Cleopatra at the battle of Actium, clearly written in 30 BCE), though it is possible some of the lighter sketches from the Greek (e.g. I.10, a hymn to the god Mercury) are contemporary with Horace's earlier Epodes and Satires. The collected odes were first published in three books in 23 B.C.
I.3 Sic te diva potens Cypri, a propempticon (travel poem) addressed to contemporary poet Virgil.
I.4, Solvitur acris hiems a hymn to springtime in which Horace urges his friend Sestius vitae summa brevis spem nos vetat incohare longam (Life's brief total forbids us cling to long-off hope)
I.5, Quis multa gracilis te puer in rosa, on the coquettish Pyrrha, famously translated by John Milton.
I.11, Tu ne quaesieris, a short rebuke to a woman worrying about the future; it closes with the famous line carpe diem, quam minimum credula postero (seize the day, trusting tomorrow as little as possible).
I.22, Integer vitae, an amusing ode that starts as a solemn praise of honest living and ends in a mock-heroic love song.
I.33, Albi, ne doleas, a consolation to the contemporary poet Tibullus over a lost love.
II.14, Eheu fugaces, an ode to Postumus on the futility of hoarding up treasure that begins Eheu fugaces, Postume, Postume, labuntur anni! (alas, the fleeting years glide away, Postumus, Postumus)
The ancient editor Porphyrio read the first six odes of this book as a single sequence, one unified by a common moral purpose and addressed to all patriotic citizens of Rome. These six "Roman odes", as they have since been called (by HT Plüss in 1882), share a common meter and take as a common theme the glorification of Roman virtues and the attendant glory of Rome under Augustus. Ode III.2 contains the famous line "Dulce et decorum est pro patria mori," (It is sweet and honorable to die for one's country). Ode III.5 Caelo tonantem credidimus Jovem makes explicit identification of Augustus as a new Jove destined to restore in modern Rome the valor of past Roman heroes like Marcus Atilius Regulus, whose story occupies the second half of the poem.
Besides the first six Roman Odes, notable poems in this collection include:
III.13, O fons Bandusiae, a celebrated description of the Bandusian fountain.
III.29, Tyrrhena regum progenies, an invitation for the patron Maecenas to visit the poet's Sabine farm.
III.30, Exegi monumentum, a closing poem in which Horace brags Exegi monumentum aere perennium (I have raised a monument more permanent than bronze).
IV.7 Diffugere nives, an ode on the same springtime theme as I.4. Contrasts between these two odes show a change in Horace's attitude with age.
IV.10 O crudelis adhuc, an ode to young Ligurinus on the inevitability of old age that hints at a homosexual relationship.