What is Copyright?
This is the legal rights held by the original content owner/creator or creators allowing the rights to. Reproduce, Distribute, Perform and creative derivatives of said piece of work. That last one means things like remixes and live versions.
There are two major aspects to note.
1 - is the publishing rights, this is the copyright of musical composition, so a songs melody can be a copyright issue.
2 - is the recorded work itself known as mechanical copyrights.
Sampling can cross both boundaries as the original musical composition can come across in a sampled work, however this is seldom the case and the majority of the time the concern will be with mechanical copyrights, The right to use that recorded piece of audio.
There's a couple of options here you can apply to the governing body in your country of origin to obtain a copyright permission to use a sample in a song (here in the UK that can be done via PRS). This can be very expensive or simply involve you giving up some of the commercial rights to your own creation that uses the sample to the original artist.
Personally the preference is to create a unique sound inspired by another and use technology to obtain that feel of the era of the sample you are trying for.
There's a whole host of ways you can use current digital audio technology to create something truly unique and self made and keep that authentic sampled sound that you are seeking without getting into the sampling conflict.
How Can i Copyright my Music?
So you created your own orginal content instead?
In most countries, copyright is attached to an original work automatically. It doesn't have to be registered, published, sold or have a copyright notice attached. The lyrics, music, arrangement and sheet music of a song each have their own copyrights. So it's not essential to register your work in order for it to be copyrighted.
Enforcing your copyright can be a whole different battle, This is where a stronger situation is created if you undergo a process to create your own copyright and register each product. As a bet maker this can be a overly expensive process. However well documents files and dates for upload etc will all hold you in good stead should a case ever be disputed as a offending party will be unable to provide the content in its original form with such vivid information to its creation.