Large Medleys Tips

[Maelstrom]

I'm planning on doing a large Kid Icarus Uprising medley next, but first, I'd like some advice on transitions between sections. Is it better to create an extra measure for a transition between keys, make it all similar keys, or just have it jump between sections?

[FierceDeity]

Well, it's all situational, really. Some video game composers already write pieces in similar keys, and some situations kinda demand it (all of the ocarina songs from Ocarina of Time, for example, are in some mode of C major, I believe). If you just have it jump between sections in unrelated keys, without any sort of transition that you come up with, then I personally don't see the difference between a "medley" and playing a bunch of pieces in close proximity to one another. In my opinion, writing a medley is a great chance to work creatively with a bunch of themes/chord progressions that you already know you like. Making them work with each other, and with whatever instrumentation you're writing for, is the fun part, the only thing that differentiates between boring transcription and actual arrangement of a medley. So, to address your questions specifically and not just make this an arbitrary, elitist rant about the inaccurate naming of "medleys" put on youtube nowadays:

Is it better to create an extra measure for a transition between keys

Depends. You can play with the melody and make it work with a modulation within the preexisting form. Or, you can add a tag at the end. Or, you can make your own alteration of the melody to add on. Either way, if you're changing themes completely, it's advisable to use some sort of modulation, as changing every aspect at once doesn't make for a very coherent piece. I'm gonna go with my advice for a lot of music-related stuff: play around, see what works.

make it all similar keys

You can. Like I said before, they often are already in related keys of some sort. But if they're not, and, say, one piece is in C, and another is in F#, feel free to change a key. Not always to the same key; dominant or subdominant is an easy switch, and depending on the relative energy of the two pieces, can contribute to that distinction even more. You can give the entire medley a sort of harmonic arc; first and last pieces in the same key, follow a progression between them.

just have it jump between sections?

Technically you can do whatever you want. As far as I can tell, you can do a medley without consideration for any of these things, and still acquire massive popularity (though, I guess this also has to do with the awesomeness of the instrument). But "medleys" that just jump from section to section with no transition, to me, really don't seem like anything more than "hey look I just plastered together a bunch of shit that somebody else wrote".

[Maelstrom]

Thanks! I'll probably make something way too long, but I'll try to be creative about it. It's just that the soundtrack is good, but it can easily be condensed to a few phrases from each song. It may be too much, but my first goal is to get something in from each of the 24 levels. (I may skip a few) I'm on vacation now, but I'll probably start choosing the clips now.

[Jompa]

I've done a bunch of medleys, and I remember back when I did the first one (a 15 minute Zelda medley) I had those exact same questions as you asked now! I spent days checking out these things.

When it comes to keys and modulations:
When changing between two songs you have two options; modulate or not. If you modulate, it will be noticeable, and that is totally fine. It is a different song after all. But the effect of having two or three songs in a row in the same key can also be really great!
An example:
You remember Serpent Devouring the Horizon, right? I don't know if it's a medley or just a big clash of original themes, but it still modulates a lot when changing between them. But somewhere in the middle there are at least four different songs in the key of B right? The one with a recorder, the one with the violin in 3/4, the soprano sax one, and then it stays that way for the next part too (though different modes and tonal genders, it doesn't modulate).
This is actually a good effect, don't you agree? They don't feel like such different songs, when this is done, and in this case it was pretty cool.
It's all a matter of what effect you want. As it is with nearly everything we do in music.
A technique you can use if you are going to modulate is by putting the dominant to the new key inn right before the modulation. That way the modulation will be a little more prepared, which can make it more discreet.
You can easily add extra measures to have a good transition, or you can be creative in other ways. Personally, I am more interested in seeing a good arrangement of the different songs together, than seeing the plain old songs someone else made.
You said you might just arrange short parts out of the songs. If you're gonna do this, then the songs will probably change pretty fast. If that's the case you might wanna try a bunch of that "keeping it in the same key"-thing, like Serpent Devouring the Horizon did with it's fast-changing part. If you're gonna modulate here it might make it a bit weird.
You remember I made that 21.5 minutes long Pokémon Suite? Here I had many songs in a row in the same key so that I could make the transition between them feel natural, which was the effect I wanted for most of them. I didn't modulate too much - I mainly modulated when I began a new movement, so it wasn't like I cared about the effect or anything like that.

Fierce is right. You can do what you want, but it won't be all too good without transitions.
The best thing you can do is to be creative!

[FireArrow]

Hey, there's way to modulate without it being very noticeable.

[JDMEK5]

Heh, whenever I end up bumping up a key, I never dilute it for subtlety. I milk it for everything it's worth.

[FireArrow]

I dunno, it's always cool when you're arranging music and there's all these modulation you never knew about just from listening to it.

[JDMEK5]

That's very much true but I rarely do it myself. Mind you I don't arrange a whole lot of medleys either. Usually it's a modulation within the same song. In which case I like my method.