Compose and comprise seem like mischievous brothers who are opposites but masquerade as each other to fool their friends. They’re very similar — both handle parts-to-whole relationships — yet they’re mirror images in how they handle it.

The standard division is this. Compose has the parts as the subject and the whole as the object. Comprise makes the whole the subject and the parts the object. So we get:

(1) [...] Pickwick was able to cultivate a sound that was more organic and unique to the six members that compose the band.

(2) The band comprises singer/guitarist Erlend Øye of Kings of Convenience, bassist Marcin Öz, drummer Sebastian Maschat, and Daniel Nentwig [...]

But is this a real distinction? I was tempted to say that it must be, because it seems like everyone knows about it. But then again, a lot of people have trouble maintaining this distinction, and I regularly see comprise used in sentences like (1). And, if I’m being perfectly honest, sentences like (2) sound rather odd to me, even after I’ve assured myself that they are appropriate. So is there a true distinction that people happen to be bad at maintaining, or is the distinction just another spurious one to add to the heap?

Well, the distinction clearly exists in one direction; while many people could use comprise in sentence 1, very few would use compose in sentence 2. As a result, we’re running into a similar situation as with jealousy/envy or verbal/oral. It’s not a matter of whether the two words are synonymous, but rather a question of whether one is more general than the other.* As usual, here’s the table of known possibilities:

whole-to-parts parts-to-whole
comprise YES (2) ? (1a)
compose NO YES (1)

Can comprise take parts as its subject and the whole as its object? Well, it’s easy to find people who say no, both on the Internet and in usage guides.

But I find it interesting that even committed prescriptivist writers, who completely believe in this rule, have trouble remembering it. Here’s a quote from William Safire:

I wrote [...] ‘They comprise a terror coalition’ [...] Greg Walker of the International Association of Chiefs of Police blew the whistle on this one, suggesting that I should have written constitute, meaning ‘make up.’ He’s right.”

And likewise, from James J. Kilpatrick:

The rule here is that the whole comprises the parts, and the parts compose the whole. [...] My problem is that I cannot seem to remember this.”

So, many grammarians want there to be a distinction, but even they have a hard time maintaining it. Does it exist in the language-at-large? It doesn’t seem to, judging from the Corpus of Contemporary American English:

527 singular-subject comprises
468 plural-subject comprise

In current usage, comprise is appearing in senses (1) and (2) almost equally.** How about historical usage?Well, interestingly, the earliest complaint about the misuse of comprise found by the Merriam-Webster Dictionary of English Usage wasn’t until 1903. But comprise was being used both ways well before that. The OED has examples from 1794 and 1799 on through to the present day. MWDEU notes that this usage was labelled “rare” in earlier editions, but this label has since been removed. So for at least two centuries, comprise has had a parts-to-whole usage that has only been gaining in popularity.

But why would comprise allow the two different usages? Well, why wouldn’t it? There’s very rarely a situation where it’s unclear which is the whole and which are the parts. And there’re parts-to-whole situations where compose doesn’t quite sound right to me, but comprise does. For instance, this MWDEU example from 1916:

“[...] the ringlets and bracelets did not comprise the whole of this young man’s soul.”

"So fellas, is it fair to say that we comprise an awesome band?"

All that said, there’s no denying that many people have a strong conviction that compose and comprise are mirror images. Although one can justify the use of parts-to-whole comprise, it’s an uphill battle. I wouldn’t recommend using it unless you’re spoiling for a fight. But if you are, you’ve got a pretty solid argument up your sleeve. The final table, with the grey indicating this “yes, but…” situation:

whole-to-parts parts-to-whole
comprise YES (2) YES
compose NO YES (1)

[For more on these words, check out Arrant Pedantry and Language Log's takes, which talk more about the passive forms than I did.]

*: I’ve taken to calling these “asymmetric pairs”, but I’m sure there must be a better name out there.

**: If you’re interested in the details, I searched the part-of-speech labelled COCA for singular or plural nouns ([*nn1*], [*nn2*]) followed by comprises or comprise, respectively, and summed over all different nouns. For a baseline (in case singular or plural subjects were generally more common), I also searched for compose. The results were very noisy due to overlap with other senses (e.g., “he composed himself before speaking”, “she composed a symphony”), but there were 40 singulars to 84 plurals in that search.

It’s worth noting that the (perhaps surprisingly common) presence of plural subjects for comprise in COCA is not driven by spoken examples. Only 19 of the hits come from spoken data; magazines and academic writing supply the bulk of the examples for both kinds of subjects. It’s appearing in edited writing, not only in unedited speech.