Nasty

Once you start listening for it, you’ll be amazed at how much music in games is simply a clunky crossfade from one piece to another. The problem with transitional forms is of course that we don’t know when a particular event is going to take place. Any of the following relationships between the two pieces of music are possible.

By choosing to use transitional music, we’re hoping to take advantage of the potentially greater emotional impact that can be produced by moving from one piece to another (rather than simply changing the mix between layers), but if we don’t do this right (i.e., musically), then this impact is at best lost and at worst becomes jarring and unpleasant, defeating the purpose of choosing a transitional form in the first place.

Open the Offices01 level and play through the first couple of rooms from *Offices Room 01* (Bookmark 1). You’ve been tasked with stealing blueprints of the latest innovation from the shadowy Nagasony Corporation, whose hi-tech offices overlook 2050 Tokyo. Stealth is key. The transition from *Offices Room 01* to *Offices Room 02* is an example of simple location-based switching, where different pieces of music are associated with specific locations.

When the levels starts, the {Room_01} looping wave starts, then a [TriggerBox] on entry to *Room 02* <Stops> this and plays {Room_02} (an only slightly nicer <Fade Out> finishes this second piece as you get to the top of the stairs).

<Play>, <Stop>, <Fade In>, and <Fade Out> can of course be used to control music for any event in the game, but there are better, more musical ways, and more musical means more satisfying for the player (having said this, sometimes bad music transitions can work for shock value).

Crossfades (and When to Use Them)

In some circumstances a simple fade in/fade out crossfade between tracks can actually work effectively, but you need to carefully consider the musical style in order to allow for a range of very different outcomes depending on the player’s approach.

If your music is quite ambiguous, then you can crossfade between one track and another without it sounding too clumsy. People will notice if a rhythm is interrupted, they will notice if a chord sequence never gets to resolve, and they will notice if a melody is left hanging in space. If none of these things were there in the first place, then you won’t have set up these expectations. So just avoid rhythm, tonality, and melody?

There are a few genres that can suit this kind of approach, the easiest being the kind of atonal soundscape typical of horror-style music, but other drone-like ambient or even very flexible cartoon-like music can work alright. It’s all about having the system of how you’re going to implement the music in mind when you write or commission the music.

On entry to *Offices Room 03* (Bookmark 3), another cue starts {Ambiguous_03}. As you will note this is very harmonically static, with only a subtle sense of pulse. When we interrupt it by crossfading to a new piece (press E by the computer in the office on the left to switch on the lights), it feels reasonably smooth since there is not a strong musical structure there to be broken in the first place.

Masking Transitions

Another very effective way to avoid musical clumsiness in transitions is in effect to hide them. A loud sound or a piece of dialogue that temporarily ducks the music can be a good opportunity to swap out your music without needing to resort to more complex systems since they will mask the clunky transition.

Once the lights are on in *Offices Room 03* (Bookmark 3), you can plant the explosive device on the door to enter the next area. Musically there is a simple <Fade Out> of the previous piece when the next music system starts, but this is masked by audio that builds up to a large explosion.

This masking effect can be helped by some quick ducking of the music in the mix (we’ll be looking at mix changes in Chapter 08). Like crossfades, this can work perfectly well in the right circumstances, but when the music is more exposed, we need to look at how we can better control when it changes.

Transitioning on Measure in Longer Pieces

Sometimes you’ll want to be able to use longer pieces of music with a more extended musical structure but still transition musically.

Rather than having the music in chunks that are retriggered, we will allow the music to play through much longer loops. We will still keep the <Timeline> events on measure but only let them through when we want to trigger a transition to a new cue. We do this by inserting a <Gate> between the <Timeline> and the <Switch>. This <Gate> will remain closed (i.e., it will not let the trigger pulse through) until a game event calls a change. This will open the <Gate> and, after the next available trigger has gone through, immediately close it again.

In *Offices Room 05* (Bookmark 5) there are a number of laser sensors that you need to avoid, carefully timing your movements around the room to make it to the exit. If you accidentally get caught by one, then you have a few seconds to make it back to the start of the room and hit the reset button before the room fills with deadly gas.

You can see below how the game events (enter room, trigger laser, reset, and reach the end) <Set> a track to play and open the <Gate>. When the next <Timeline> event comes through, the <Sequence> object on the right will apply a short fade to the currently playing track and play the new one.

This time we have used a -Switch- inside the Sound Cue. Since we are now using longer pieces of music, we don’t have the need to be picking randomly from a series of chunk variations. (Alternatively you could set up an Array of cues like you did for exercise 05_01 if you have lots to deal with.)

When the game events happen, the variable Trans_On_Measure is set and the <Gate> opened so that the next bar line event from the <Timeline> can go through. This first triggers a <Fade Out> of the track that is currently playing and then triggers the <Play Sound Attached>. This has a <Set In Parameter> attached that will take the value of the variable Trans_On_Measure and use it to set the Transition_Measure parameter that controls the -Switch- inside our Sound Cue. Using this method we can use longer pieces and then transition on the bar line to the start of a new piece in response to game events.

Pre-syncs or Ramps

The problem with transitioning on the next measure or bar line is that, although it may be musically satisfying, the music can sometimes feel like it’s not reacting quickly enough to acknowledge game events. When an event happens, particularly one significant enough to warrant a transition rather than just a stinger, we want the music to acknowledge it immediately, but of course this brings us back to the issue we highlighted at the start of this chapter—the irreconcilable differences between arbitrarily timed game events and musical events.

A good solution to this is to use a pre-sync cue. This is a music cue that we can start to fade in immediately once an event has happened and which builds towards the actual transition, thus heightening its impact even more.

For example think about a bar/measure of music with a snare drum in eighth beats (quavers) getting louder. If this was synced to the current measure, then we could start to fade it in at any time, it would still work as a build up to the transition, and because it can start to fade in immediately, we will be giving the player an immediate acknowledgment of their actions or the event. Another name for this might be a ramp track, a one-bar measure that ramps up to an oncoming transition.

Go to the “Room 05” section of the [Level Blueprint], uncheck the box on the <Gate> in the Pre-Sync section so that <Gate> now starts as open, and play this section again. Hopefully you can hear that this is more satisfying.

As you can see this is pretty simple to set up. The one measure pre-sync cue referenced by the <Play Sound Attached> is actually played at the start of every measure from the <Timeline> so that it is in sync (you might think of this as a parallel approach—and you’d be right, but we’re talking about it here because its use is in pre-empting transitions). Its volume is immediately adjusted to 0.0, only to be faded up by the other <Adjust Volume> node when the event happens (in this case the call to transition to the higher intensity track). The <Gate> is simply there so that you can switch this system on and off to hear the difference. You could also have another pre-sync or ramp track that leads into a transition down in intensity.

Exercise 05_03: Transition on Measure and Pre-sync

Once you have got past the courtyard, you enter the *City Streets*, a warren of alleyways. You must find three items in this location in order to bribe your way into the inner courtyard of the city. Unfortunately some of the alleyways have been rigged with trip wires that will bring the soldiers running! In this exercise you will create some longer tracks that transition on measure when there is a change of event together with some pre-sync cues to acknowledge them immediately.

1. As before this is a complex system, so we have set most of it up for you.
2. Write 4 tracks: {Stealth}, {Action}, {Triumph}, and {Death}. The {Stealth} and {Action} cues can be longer this time (but still the same tempo). The {Triumph} and {Death} should be one measure/bar long.
3. Now write three pre-sync cues. One that will lead from {Stealth} to {Action}, one that will lead from {Action} to {Triumph} and one that will lead from {Action} to {Death}.
4. Edit the {Streets_Music} Sound Cue and replace the 4 placeholder files with your own. Make sure that you connect the correct ones to the appropriate inputs of the -Switch-.
5. Add your pre-sync tracks to the appropriately named <Play Sound Attached> nodes.
6. Remember you may need to edit the length of the <Timeline> to match the length of a measure for your tracks.

Aligned Transitions

We can transition immediately, but to a time aligned position in the other track rather than the start of a new track, in order to maintain musical continuity between what might be different arrangements. To do this immediately would feel exactly the same as a parallel approach where we have the two synced cues running but then fade one in and the other out (the advantage would be that we are not actually playing the second track—thus saving that voice for something else).

What we are interested in here is transitioning to and from musical junctures. We won’t look at transitioning immediately, but instead will consider what to do if we want to move to a new track that is aligned in time but on a bar line (you can transition immediately if you wish—simply remove the <Timeline> and <Gate> from the following system).

You might use this system if you have two arrangements of the same piece of music, perhaps one full and intense, the other more lyrical and full of yearning (or something like that). When events change you want to maintain the musical and harmonic flow, but swap to the different arrangement that perhaps has different instruments. You don’t want to do this instantly (through a parallel approach), but instead want the change to happen on a bar line.

In *Room 06* (Bookmark 6) there is another laser security system, and again you must time your movement through the room to avoid the lasers or else the poisonous gas is released.

In order to transition to the same point in the new track that we are at in the currently playing track (although we are going to restrict this to happening at bar lines), we need to set up a timing system. We have done this using a <Set Timer> node. The length of this is set to when we want our tracks to restart. Remember this is not necessarily the exact length of the track since the track may include a decay tail at the end. The timer outputs a <Custom Event> called Music_Length (as defined in the Function Name) when it reaches this time. This means we have got to the end of the track, so this goes through and starts the timer (and triggers the <Play Sound Attached>) to loop the track around again. (Note that unlike the previous {Transition_Measure} cue this time the {Transition_ Aligned_Measure} does not contain -Looping Wave Players- since we are looping the cue with the <Timer> in order to better maintain the sync for the aligned changes.)

Just as before, the events in the game (getting caught by a laser and resetting the security system with the button by the door) set the variable that we are using to control the -Switch- in the Sound Cue. The difference is that now our <Play Sound Attached> does not start playing the new track from its start. Attached to its Start Time input is the current value of our timer. So the new track will start playing at exactly the same time point that the old track was at—hence we are moving to an aligned point in the new track!

However, the changes are still only initiated when the <Timeline> event comes through, so we are aligned to the same point in the track but only actually transition to it on the next bar line.

Putting It Together

We’ve covered several approaches to transitional forms that you can obviously combine and adapt to the particular needs of any game you’re working on. In *Room 07*(Bookmark ‘7’) we put together a system that combines some of the things we’ve been talking about. You can have a look at the system in the [Level Blueprint](“Room 07 Music” section) but we will just describe how the music works and then you can get on with the exercise.

Note that none of these systems has absolutely perfect timing given that UE4 does not yet have a sample accurate audio system- however this is promised in a future update!

This is an implementation of the system we started the chapter with.

The player needs to get around the room to use three switches to open the safe where Nagosony’s darkest secrets are held. There are some security turrets on the ceiling which are triggered by the cameras and lasers. Luckily there are some fortuitously placed dividers around the room that you can hide behind to wait until the systems stand down.

The music operates as defined in the following transition matrix: