The top level of a piece of music written in Alda is the score. A score consists of any number of instrument parts, each of which have their own note events, which occur simultaneously.
Alda is designed to be flexible about how a score is organized. For the same piece of music, a composer can choose to write each instrument part's notes from beginning to end before moving on to the next instrument part (something like ex. 1), or alternate between the instrument parts, organizing the score by section rather than by part (ex. 2).
Note: Here is a list of instruments available to you when writing a score in Alda.
Ex. 1
trumpet:
o4 c d e f g a b > c d e f g a b > c
trombone:
o2 e f g a b > c d e f g a b > c d e
Ex. 2
trumpet: o4 c d e f g a b > c
trombone: o2 e f g a b > c d e
trumpet: d e f g a b > c
trombone: f g a b > c d e
Under the hood, Alda processes a score sequentially, keeping track of information about each instrument, including the instrument's volume, tempo, duration, offset, and octave. The nice thing about this is that, when switching to another instrument and then switching back, you don't have to worry about changing the volume, tempo, octave, etc. back to what they were when you were last using the instrument - Alda keeps track of that for you.
It's possible in Alda to use the same note events for multiple instruments at once by grouping them, e.g.:
trumpet/trombone: c d e f g f e d c
Keep in mind that Alda is still keeping track of each instrument's volume, tempo, octave, offset, etc. separately, which means it is up to the composer to ensure that the instruments are playing in sync, if that's what the composer wants. In ex. 3, the trumpet plays some repeated D notes at the start of the score, then an ascending D minor scale; the trombone also plays the D minor scale, however it starts at the beginning of the score, so it beats the trumpet to the punch. Ex. 4 shows a way to remedy this situation, in cases where the really want both instruments playing in unison. Ex. 5 shows another way to achieve the same effect using markers.
Ex. 3
trumpet: d d d d d d d d
# not in sync, trombone starts earlier
trumpet/trombone: d e f g a b- > c d
Ex. 4
trumpet: d d d d d d d d
trombone: r r r r r r r r # (rest for 8 beats)
# in sync
trumpet/trombone: d e f g a b- > c d
Ex. 5
trumpet:
d d d d d d d d %scaleTime
trumpet/trombone:
@scaleTime d e f g a b- > c d
Alda chooses not to force instrument parts to sync up when used as a group in order to allow composers the freedom to experiment with multiple instruments playing the same notes in different ways. For example, you could give the instruments different tempos and/or note durations and have them play the same notes:
Ex. 6
violin: (tempo 100)
viola: (tempo 112)
cello: (tempo 124)
violin/viola/cello: e f g e f g e f g e f g e f g
So far, we've talked about using different types of instruments at the same time. But what if we want more than one of the same instrument? Let's say we're writing a piece of music for two oboes. We obviously can't refer to them both as "oboe"; how will we tell them apart? That's where aliases come in.
You can give an alias to an instrument by putting the alias in double quotes after the name of the instrument:
oboe "oboe-1":
c8 d e f g2
Now oboe-1 refers to our first oboe. From now on, to tell oboe #1 what to do, we must refer to it as oboe-1, not oboe.
oboe can now be used to create a second oboe:
oboe "oboe-2":
e8 f g a b2
You can also alias a group of instruments:
oboe-1/oboe-2 "oboes":
> c1
When an alias is given to a group of instruments, the individual instruments can
then be accessed via the dot (.) operator.
This can be useful when you create a group of unnamed instances, and you end up wanting to use the individual instruments later:
violin/viola/cello "strings": g1~1~1
strings.cello: < c1~1~1
Instrument names and aliases must adhere to the following rules:
- They must be at least 2 characters long.
- The first two characters must be letters (either uppercase or lowercase).
- After the first two characters, they may contain any combination of:
- letters (upper- or lowercase)
- digits 0-9
- any of the following characters:
_ - + ' ( )
The details of how Alda creates and assigns instrument instances are complicated, but for practical purposes, you can avoid errors by following these simple rules:
-
If you assign an alias to one instance of an instrument, then any other instance of that same instrument in your score must also have an alias.
# ERROR piano "foo": c8 d e f g2 piano: e8 f g a b2 # ERROR piano: c8 d e f g2 piano "bar": e8 f g a b2 # OK piano "foo": c8 d e f g2 piano "bar": e8 f g a b2 -
Once an instance is aliased, you cannot give it a new alias.
# ERROR piano "foo": c8 d e f g foo "bar": a b > c # OK piano "foo": c8 d e f g foo: a b > c -
You cannot reassign an alias to another instance.
# ERROR piano "foo": c8 d e f g2 clarinet "foo": e8 f g a b2 # OK piano "foo": c8 d e f g2 clarinet "bar": e8 f g a b2 -
When making a group, every member of the group must be either a) a new instance of an instrument, or b) an existing instrument with an alias.
Combining the two is not allowed because it can lead to situations where it isn't clear which instrument instance should be used.
# ERROR piano "foo": c8 d e foo/trumpet: g1 # OK piano "foo": c8 d e trumpet "bar": r8~8~8 foo/bar: g1 # OK piano/trumpet: c8 d e g1