I believe you would violate laws not once but plenty of times doing so.
Copyrights laws are mostly approved all over the world. Independently from where you live, they are mostly the same. For more details, google can point you to the correct site for your country.
A song can't be redistributed, in any form or shape, unless approved by whoever retain rights for that song (producer, composer, group, whoever is). Listening on the radio, means that the radio station paid the rights to play it, and you can only listen to it...ripping it, like you do with youtube videos, is a violation
Take out part of the song, is also illegal; "sampling", which is the term used to get a piece of a song to make a loop (like some hip hop artists loved to do in the past), is legal only if you have the authorization; 2nd infraction.
Then you want to strip the instrumental track, which beside being pretty difficult, since the instrumental track is merged with vocals and back chorus, but even if a software does extract it for you; this is yet another infringment of the law; unless you are authorized to do so (in which case, you would get directly the instrumental track from the producer, they record in multiple tracks for flexibility).
At last, after that you broke 3 times the copyright law; you put it in your product, without authorization, which is the 4h and last infraction.
- ripping is illegal
- sampling is illegal
- modify a song to extract the instrumental track is illegal
- use a song or part of it is illegal
Solutions: either make your own loops, hire a musician to write the score or request the artist permission; unless you deal with U2 or Metallica, indie artists are friendly people, that may even end up giving you the rights in exchange of a bit of royalties based on your sales.