Game music

[kelp7]

Hi,

I've always wondered how the programming for in-game music is achieved. Does the programmer set up an interrupt that jumps to a music routine? Or do you manually jump during the vertical blank? How does the music regulate its tempo if you are just manually jumping every 1/50th second to a music routine?

Thanks!
kelp

[malcontent]

It is usually jsr'ed to in the IRQ. Tempo wise you have a decent amount of wiggle, as in practice you'll be holding notes; even a sixteenth note needs to be sustained for several screen refreshes.

Music is done using tables, with values to feed into the registers, and a value to determine length. Each time the routine is called, the length is decremented or compared, and if it's over, the next note/length in the table is grabbed.

[Kweepa]

Here's an example, from Doom:
https://github.com/Kweepa/vicdoom/blob/ ... laysound.s
It works pretty much as malcontent describes.
I didn't change the interrupt frequency away from its default 60Hz.

[tlr]

If you require raster splits for graphics purposes in your code then it's a good idea to also call the music synchronized with the screen update.

I tend to do that always unless there is a specific reason.

[kelp7]

As ever I applaud this forum and its forumites always receive many a helpful answer when I pose these (probably newbie) questions...
thanks!
kelp

[kelp7]

Actually, on a similar topic to this (and bear with me because I really am pretty new to writing games). Sound effects in games, are these done in a similar way to the music? In my younger years when I did actually try writing my own games the sound would always stop the rest of the program, i.e. the action on screen would halt while the sound played. Obviously, I wasn't writing in machine language or assembly then... just BASIC. I'm guessing from the above answers that it's a pretty similar method to the music?
kelp

[beamrider]

Not sure about anyone else but my sounds in Pooyan are actually small tunes. I have two music players. The effects player steals channels from the background music as needed.

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[beamrider]

.....So I can play a sound effect or tune by just setting a value in memory that gets polled during the IRQ handler

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[Mike]

[...](and bear with me because I really am pretty new to writing games).[...]

Really?

http://sleepingelephant.com/ipw-web/bul ... php?t=2904

... and to quote from this posting in 2008:

I [...] am going to jump straight in at the deep end with machine language rather than BASIC. (Simply because i've written other games in machine code on other machines).

Sorry, but ...

[Kweepa]

Doom's sound effects are similar to the music - the code is in the same file.
I use the noise channel exclusively for sound effects, but I pause the music because the volume for the effects needs to be cranked up to be heard.

[tokra]

Would it possible to do it like this?

- first interrupt cycle silents noise-channels, sets volume to 8, plays music note
- second interrupt cycle silents music-channels, sets volume to 15, plays noise channel
- repeat

No idea if that would sound as one would expect (low music, loud noise).

[kelp7]

[...](and bear with me because I really am pretty new to writing games).[...]

Really?

http://sleepingelephant.com/ipw-web/bul ... php?t=2904

... and to quote from this posting in 2008:

I [...] am going to jump straight in at the deep end with machine language rather than BASIC. (Simply because i've written other games in machine code on other machines).

Sorry, but ...

Haha, yep. I'd still consider myself a newbie. Any 'games' I may have written before were pretty basic themselves and I understand a reasonable amount of programming theory (iteration, jumps, etc) but there are plenty of things I still have no clue about Scary how much time has passed since writing that and I still never found time to properly get into all this. However, that said, I now do have some amount of time to dedicate to writing stuff. I have said in another thread here that I'm currently writing for a different machine than the VIC but I come here to ask questions as this is an extremely helpful and active forum! I do actually intend to write for the VIC in the not too distant future. Heh, sorry for the contradictory-sounding posts!
kelp

[kelp7]

...and thanks everyone for the rest of the replies! Very helpful and does shed light on how these things work...