File the two applications for the same song on the same day and, in our experience, the musical work comes back meaningfully sooner. It is worth understanding why, because it changes how you sequence a release.
The recording simply has more to check
A musical work filing has composers and lyricists, a deposit copy you produced yourself, and an author column with an uncontroversial answer.
A sound recording filing has all of that behind it, the composition is embedded in it, plus an arranger, plus every performer with rights of their own under section 38A, plus an author column where the correct answer is a defined legal term that most applicants get wrong the first time.
More parties means more consents. More consents means more that can be missing or badly drafted. And the author column on the recording is the one that draws clarification requests.
What follows from it, practically
File the musical work first, or at least at the same time. The recording filing sits on top of the composition. Being able to point to a registered underlying work strengthens the recording application and gives you something concrete if a query arrives.
Do not read the gap as a problem. Seeing one registered and the other still pending months later is the normal shape of things, not a sign the second has failed. Rejection arrives as a letter; silence is a queue.
Budget attention accordingly. If you have limited time to get paperwork right, spend it on the recording side. The composition filing tends to look after itself once the composers have signed; the recording is where the effort pays.
Expect the recording to cost more. The fee is charged per work and is higher for a sound recording, so a two-filing song is not double the cheaper fee.
The sequencing that works
Get every consent signed and notarised in one sitting, while everyone is reachable and well-disposed, that is the step that decays fastest as time passes. File both applications. Post both packets inside the window. Then stop refreshing the portal for a few months.