I have a theory which I can't prove, but which I'll rehearse here, in the decent obscurity of this blog. I think that Shakespeare was a thrifty writer, and prone to reusing ideas, lines, bits and pieces. More, I think that, when he sat down to write Twelfth Night in 1600, he found an old scrap of paper upon which was written a sonnet, or notes towards a sonnet: one that he'd started but not completed to his satisfaction back in the 1590s. I think that he repurposed this abortive sonnet into the opening speech for his play, swapping some of the lines around, cutting some of the rhymes (which would otherwise be too obvious and clanging) and adding a line:
IF Musicke be the food of Loue, play on,!The first eight lines of this form a sort of octet, and the final seven an elongated sestet, with the turn being the shift from addressing the musicians (to instruct them to play) to addressing the ‘Spirit of Love’ directly. Now, it might be that this, in the very broadest sense, ‘sonnet’ pattern is discernible because that's the way Shakespeare's thoughts naturally shook themselves out when writing, as here, about love. But it's also possible that his desk drawer contained, with various foul papers and drafts, a sheet upon which was written something like this:
Giue me excesse of it: that surfetting,
The appetite may sicken, and so dye.
That straine agen, it had a dying fall:
O, it came ore my eare, like the sweet sound
That breathes vpon a banke of Violets;
Stealing, and giuing Odour. Enough, no more,
'Tis not so sweet now, as it was before.
O spirit of Loue, how quicke and fresh art thou,
That notwithstanding thy capacitie,
Receiueth as the Sea. Nought enters there,
Of what validity, and pitch so ere,
But falles into abatement, and low price
Euen in a minute; so full of shapes is fancie,
That it alone, is high fantasticall.
If musicke be the food of Love, play aye!... or something along those lines.
Give me excesse of it: that surfetting,
The appetite may sicken, and so dye
Into suche joy as lovers sighes yett bring.
Play straines agen that have a dying fall:
To come upon my eare like the sweet sound
As breathes upon a banke of Lilies tall
Stealing and giving Odour in the rownd.
O spirit of Love, thou art so quicke and farre
That notwithstanding thy capacitie
Receiveth as the sea, nought entreth there
But drops into a low validitie
E'en in a minute; fancie so shapes its fall,
That it alone is high fantasticall.