I'm about to release an EDM single (trance) that features a guest vocalist (who recorded himself and sent me the files). What are the most common ways to setup the remuneration in this scenario?

1) Give the vocalist a percentage in the contract?

1b) If so, how much is reasonable? (The song is mainly instrumental with a vocal chorus.)

2) Or maybe a single-sum buy-out on the side? (Probably not worth it, as I'm not making any money on this ...)

Grateful for any insights about this!

Either is acceptable. Best way is to negotiate with the singer and write up a bullet proof contract between you.

If you are going to pay him/her a single sum then you need to make sure that the contract states that you have bought the rights to this performance as a recorded medium and that you have therefore acquired all the associated rights otherwise he/she could theoretically still demand royalties.

If you are going for the percentage work out roughly what percentage of the song is the vocal. Did the vocalist write any lyric or was it a composition that you asked them to record for you? If they did write anything then you need to agree a publishing split as well as a performance split with regards to percentages in the contract.

If this is your first collaboration together and you think that the piece is good and that you might work well together in the future I would stick near the 50/50 60/40 arena. If you feel that you put in most of the work and that you could easily use another vocalist go 75/25 80/20

The absolute minimum you should offer if they have written any lyrics is 10%

You also need to consider whether or not you will be reusing the vocal recording in any other piece or remix and make that clear in the contract.

Thanks for your extensive reply, very helpful!

A label has expressed interest in signing the track, so the perf/mech splits between me (composer & producer), a lyric collaborator and the vocalist should all be specified in the contract with the label directly, right? (I'm not going for the vocalist buy-out option.)

The label has given me 50/50 in the past for my solo releases, so now the contract could state 50% for label, 30% to me, and 10% each to my to collaborators?

Sorry if my questions are silly, I've never signed any collaborations before and want to make sure I understand correctly...

Yep. That adds up to 100%

As long as you've taken into account everyone who has contributed to the track and either paid them off (and had them sign on the dotted line to that effect) or offered them a percentage (again, signed and sealed) you should be laughing. Hope the track does well