Great lyricists? Bah! Humbug! In the 1960s and 70s, I battled students who wanted me to teach Bob Dylan rather than Donne or Yeats. Ever since, I have had screeds of stuff sent to me by people who thought that rhyme equalled reason, to whom I had gently to explain that their agonised posturings wouldn't pass for poetry. I blame Dylan. In my eyes, he wasn't fit to tie Woody Guthrie's shoelaces. I have never forgiven him for keeping his fans waiting at the Isle of Wight festival in 1969 for three hours, from 9 o'clock till midnight, before he would sing a word. Creeps sometimes make good poets, but Bob Zimmerman isn't one of them.

And Madonna, she still has not showed

We see this empty cage now corrode

Where her cape of the stage once had flowed

The fiddler, he now steps to the road

He writes ev'rything's been returned which was owed

On the back of the fish-trucks that loads

While my conscience explodes ...

(Visions of Johanna)

Fustian of this ilk crosses my desk every week. It's not verse, not even doggerel. Nor is it prose, because it doesn't make sense. Its combination of pretentiousness and illiteracy isn't surprising, which would be something; it's just annoying. God knows why the texts put to 20th-century music began to be called lyrics rather than words. Words is fine with me. Historically, a lyric is a poem in song form, and poets from Wyatt and Surrey to Heaney have been very good at writing them. Many of our best lyrics were written for music, some of them dittied - that is, written to be sung to a pre-existing tune. Others are songs that carry their music within them. Blake's Songs of Innocence and Experience is his undisputed masterpiece, and five minutes with this tiny sample will show why:

O rose, thou art sick.

The invisible worm,

That flies in the night

In the howling storm,

Has found out thy bed

Of crimson joy:

And his dark secret love

Does thy life destroy.

The punctuation is from the original engraving. Chances are if you set this song to music you'd get it wrong, because its own internal music would be overlaid by another music that neutralised it. Mapping the music of such an utterance is not easy, but it can be partly understood in terms of musical notation. Each line has two bars, say, but the downbeat comes on the last note of the bar rather than the first. If we think of each bar as of the value of a minim, we can see that it may contain any combination of crotchets and quavers that will add up to the minim. So the first line goes tum tum ta ta tum (crotchet-crotchet-quaver-quaver-crotchet), the next ta ta tum ta ta tum, and so on. This pattern overlies another pattern of recurring sounds, one in the paired vowel sounds, like the tolling "O rose" (bong bong), a tocsin to begin the poem, followed by eye-eye, ow-ow and oy-oy, and the anxious clickety-click of the short vowels in between. Yet another kind of patterning can be discerned in the slithering interplay of voiced and unvoiced consonants, which acts like a dynamic, speeding the utterance up and then slowing it down. The singer-songwriter transforms his words in the way he writes the music and the way he sings his song; Blake's achievement is to encapsulate the entire process in silence.

The other aspect of a lyric is its mystery. A lyric does not explain itself, nor does it tell a story, except by implication. Blake's song is an invocation, to whom or what we do not know. Is the rose a hedgerow flower or the mystical rose or the barmaid at the Rose and Crown? The poem is as simple as may be, being composed of three sentences, the first and third simple and the middle one with a subordinate clause. The words are all common: we know what each means but not what is meant by them together. The theme of love and death that permeates our entire literary tradition lies coiled upon itself in this tiny poem, capable at any moment of setting off a chain reaction in the mind.

When Morrissey sings a Morrissey song, he knows exactly what colour every part of every word is meant to be, and whether it crosses the rhythm to build up tension, or cannons into it to gain emphasis. If Morrissey repeats a line, he may vary it in a new context, or he may keep it exactly the same, as he does with "Every day is like Sunday", because part of the point of the song is the anguish of monotony as perceived by hapless youth - but the music catapults the repetition towards us like a javelin. The music does what the words alone cannot do. To present the words without the music is to emasculate them.