Yes, it is legal to promote your music on SoundCloud, as long as the music you upload is original and you have the necessary rights to distribute it. You should also make sure that you are complying with SoundCloud’s terms of service, which prohibit the uploading of copyrighted material without permission.
It’s worth noting that there may be some legal considerations when it comes to using samples or other copyrighted material in your own original music. If you use samples or other copyrighted material, you should make sure that you have obtained the necessary licenses or permissions to use that material. It’s also a good idea to consult with a lawyer who specializes in music law to ensure that you are fully compliant with all applicable laws and regulations.