Send them a proper remix pack and you'll look professional — send a single MP3 and you'll look like a headache. The pack:
1. Stems as WAVs, labeled clearly: Artist_Title_Vocal.wav, Artist_Title_Drums.wav, etc. 24-bit if you have it. Every stem must start at the SAME point (bar 1) — even if that means silence at the top. Alignment is everything.
2. BPM and key. Put them in the filenames AND a little readme text file: '128 BPM, A minor.' The remixer shouldn't have to detect anything.
3. Bonus versions if you have them: instrumental, a cappella (vocal-only), and the full mix as reference. More ingredients, better remix.
4. A simple agreement. Even an email: 'You can release the remix, we split royalties 50/50, credit me as original artist.' Five lines now prevent five months of drama.
5. Keep your masters. Send copies, never your only files. And keep a note of who got what — remix packs floating around unlabeled is how leaks happen.
Good luck! Hank founder of SonorixPG