To put it simple:
1. Find a song that's in duple meter or an even rhythmic pulse you can stay on step with using your TWO feet (emphasis on the TWO).
2. Make sure the tempo stays constant throughout the whole song and is AT LEAST 95BPM.
3. It can't have vocals of any kind.
And a side note:
3. There is NO music caption on Drum Major Judge's sheet.
Set in that framework, you pretty much have an expansive variety of pieces to choose from, especially since there is no regulated genre from which your music can be attained from. It does not matter whether or not you decide on a song on the basis that it sounds really cool and awesome, AS LONG AS it agrees with rules 1, 2, and 3 and you can definitely perform your routine without it distracting you in any possible way. There should not be any debate on what kind of music is better for L-pattern, as been discussed over and over (run over a couple of times) and than over once more, it is all a matter of personal taste. Take that as you will.
Marches are straightforward. If you want to use one, just download it, take off the ending and loop it. BOOM, you're ready to go. If you wanted to take a more musically varied path, it is a tad more complicated than that. I always took several precautionary steps every time I chose L-pattern music to ensure myself a fool-proof piece of music that is unique but also strong enough that I could perform any routine and still stay on step in my sleep.
1. When you find your song, to take it a step further than just skipping to random sections and seeing if it worked, "imagine" your routine while lifting your feet up and down as if you were marching and make sure the beat is steady and the pulse remains the same. Repeat this step (sometimes with variations like standing up and marching around your room "fake" performing your routine if you don't have that much space) until you know you comfortable with it.
2. Figure out the tempo of the song to make sure it is AT LEAST 95Beats per Minute! The rules state that it should be at least 90BPM, but you can never fully trust technology, especially when cassette tapes are still in use for music. It may or may not slow your music down as it is playing, so there should always be some sort of buffer. You don't want to get docked for music when it's not even supposed to be a factor in your score. No-brainer there. I use an electronic metronome for this step...
3. Test run to see if there are any kinks in your song. If so, revert to previous steps or proceed to step 3a.
3a. With the advent of user-friendly music editing programs (I use Acoustica Mixcraft), there should be no reason your song shouldn't work. Too slow? Speed it up. You want it slower? Slow it down. Not long enough? Copy and paste if necessary. Too long? Splice and delete. When finished tinkering with your piece, perform a couple more test runs and VOILA! Perfect L-pattern piece.
I for one never used march music for L-Patterns, but I would still cringe when people used techno versions of "Night on Bald Mountain" (Such desecration to one of Mussorgsky's greatest classical pieces? That's blasphemous!), jazz music (swung, if I may add. How one would even march to that without your body inherently doing a little dance I do not know.), instrumental pop music, or some ambient musical piece more befitting to a trendy restaurant (or playing to imitate nature as part of some yoga or meditation class). Classical music and film score music is awesome to me. Marches are great too (as long as it isn't a march shared by the other bajillion people using marches. Seriously
)! I honestly used video game music because, well that was my style. But I tend to take things a step further and cut pieces of several video game songs and combined them for the final medley-esque and personalized and original product, almost field show-like to say the least. Still, those steps must still be taken within the foundational boundaries set for in the beginning of this post. The end result should be something like this:
http://www.youtube.com/watch?v=r7kvt07wZiA
In the end, it's everything about your spinning, routine, all that jazz and NOTHING about the music (to a certain extent). So why not make that music your own like a company's trademark slogan or jingle? Anyway those were my two cents on the subject.