Q:

I heard  . [parse]

(1) I heard Mona singing that song.
(2) I heard the song sung by Mona.

"Mona singing that song" and "the song sung by Mona" are objects, each of which can be parsed two ways: "head noun phrase + its participial modifier" or "participial clause". Is it right? Thanks!

A:

There are a number of ways to parse the two sentences, and they do have similar meanings, in that they can both be used to describe the same event. But they have completely different structures and their parses are not the same. Partly this is due to the wide range of syntactic structures available to sense verbs like hear, but also to the fact that English usually has several different ways to say anything.

(1) I heard [Mona singing the song]. (let's leave that out of this, OK?)

has a very simple Subject-Verb-Object structure. The Direct Object of heard is the gerund clause Mona singing that song, which is a noun phrase and can be an object. That's a very common construction with transitive non-volitional sense verbs: I saw him arriving, I felt him striding, etc.
The gerund clause still has its subject Mona, but it's not a participial phrase; it's a complement clause. Gerunds use -ing verb forms, which are technically called participles, but they don't form participial phrases, which are modifiers. Gerunds are used as nouns, not modifiers.

(2) I heard [the song [sung by Mona]].

on the other hand, has been transformed by Whiz-Deletion, stripping off the markers from the relative clause in
(3) I heard the song [that was sung by Mona].
and producing what's often called a truncated relative, which is a variety of participial phrase. They are modifiers, like relative clauses, and not nouns like gerund clauses.
So in (2) the speaker is saying what they heard was the song that was (or is -- tense is not available when auxiliaries are deleted) sung by Mona. It could be that Mona made the song famous, and the speaker heard someone else sing it. This is not the case in (1), where the event of Mona's singing is what the speaker said they heard. So, while they can both describe the same event in some cases, they approach the task from different directions and use different means. And different meanings.

