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[DZ-Jay]

I have what is probably a very silly question, but I will ask it anyway:  What is the actual relation of the BPM to the Speed of the song?

Here's what I know:

• Speed is the number of "ticks" representing the duration of a row.  So, a speed of 5 means that each row lasts for 5 "ticks."
• "Ticks" are the lowest unit of time in the tracker:  the state of effects, envelope, and other instrument synthesis is updated on each tick.
• BPM is another way of measuring the speed of a song, in beats-per-minute.

On my tracker (and I thought this was standard, but I'm not sure now), a "tick" is 1/60^th of a second, tied to the vertical refresh rate of the video signal (or 1/50^th of a second, on PAL/SECAM video).

So, my question is, where does the BPM fit in there if the tracker sequencing is controlled by the speed of the song, which is counted in 60Hz "ticks"?  It is not clear to me where in a pattern is a "beat," since it could be arbitrary depending on how you arrange it.

I suppose I could change the speed of "ticks" by scaling them down.  However, I wouldn't be able to make them go faster on my tracker, since the only source of timing I have is the vertical refresh signal at 60Hz.

Any insight in clearing my confusion will be greatly appreciated.

     -dZ.

[looper231]

As a reference if that might help: Most if not all C64 tunes were written on a PAL C64, meaning a 50hz refresh rate. In emulators, or even let's say "Furnace" (Another tracker) a SID will always be in 50hz mode. Hard to explain but if you line a SID playback with an another chip, you will notice that SID will sort of "lag" behind.

I think the only thing that doesn't rely on your refresh rate is BPM. from my experience listening to modules, the speed was mostly used to do a swing tempo (is that how you call it?), in other words, composers kept altering it between different values, for example

Code: [Select]

c-4 01 v64 F03
--- -- -- F04
--- -- -- F03
--- -- -- F04
--- -- -- F03
--- -- -- F04
--- -- -- F03

Amiga was PAL as well, but its speed didn't seem to rely on refresh rates? Maybe someone who is more confident in this can explain. I wasn't born back when tracking began rising, sadly 

[DZ-Jay]

As a reference if that might help: Most if not all C64 tunes were written on a PAL C64, meaning a 50hz refresh rate. In emulators, or even let's say "Furnace" (Another tracker) a SID will always be in 50hz mode. Hard to explain but if you line a SID playback with an another chip, you will notice that SID will sort of "lag" behind.

Thanks.  I was born back then, but unfortunately I was not tracking.  I was a Club DJ, so to me BPM is a very specific measurement of music tempo.  It is more "music-y," in that it is a more common term among musicians; whereas "ticks," "speed," and "rows" are purely technical things in trackers.

Intuitively (and naïvely), I feel that you either measure your track tempo by Ticks-Per-Row (Speed), or by Beats-Per-Minute (BPM), but not both.  To me, the former seems more natural in a tracker; while the latter is more natural in a higher-level production software, like Logic, etc.

As I see it, when using BPM, you would have to necessarily define how many rows fit in a "beat."  But then, there is nowhere to enter such a number in trackers, so it seems very arbitrary to me.  (I guess you can just keep it in your head, like a 4/4 signature = 4 rows per beat, 16 rows per pattern, etc.)

I think the only thing that doesn't rely on your refresh rate is BPM.

I suppose I could use BPM to compute a speed that is not a multiple of the refresh rate, like using fixed-point arithmetic to scale the refresh rate to any speed equal to, or lower.  But again, that requires you to figure out the relationship between rows and beats.

Then again, I could also be way off.  It does not help that I tend to over-think these things. 

Hopefully someone else can chime in with more insight.

     -dZ.

[looper231]

Intuitively (and naïvely), I feel that you either measure your track tempo by Ticks-Per-Row (Speed), or by Beats-Per-Minute (BPM), but not both.  To me, the former seems more natural in a tracker; while the latter is more natural in a higher-level production software, like Logic, etc.

I don't think that's the case for trackers here, because I've seen modules both with custom TPR and BPM together.

As I see it, when using BPM, you would have to necessarily define how many rows fit in a "beat."  But then, there is nowhere to enter such a number in trackers, so it seems very arbitrary to me.  (I guess you can just keep it in your head, like a 4/4 signature = 4 rows per beat, 16 rows per pattern, etc.)

There is a setting for XM to specify the number of rows on a pattern

[DZ-Jay]

Intuitively (and naïvely), I feel that you either measure your track tempo by Ticks-Per-Row (Speed), or by Beats-Per-Minute (BPM), but not both.  To me, the former seems more natural in a tracker; while the latter is more natural in a higher-level production software, like Logic, etc.

I don't think that's the case for trackers here, because I've seen modules both with custom TPR and BPM together.

Yes, I've seen that too.  That's what prompted my question -- it is the source of my confusion.  I must be misunderstanding something because in my mental model, they are separate measurements.

As I see it, when using BPM, you would have to necessarily define how many rows fit in a "beat."  But then, there is nowhere to enter such a number in trackers, so it seems very arbitrary to me.  (I guess you can just keep it in your head, like a 4/4 signature = 4 rows per beat, 16 rows per pattern, etc.)

There is a setting for XM to specify the number of rows on a pattern

That is true, but nothing tells you that a pattern is one beat -- or does it?

From what I see, if I set a pattern to 16 rows, nothing tells me how many "beats" those are -- it could be one beat, or four beats, eight beats, 16, or whatever.  In fact, I believe you can have patterns of different lengths in the same song, yet only one BPM at any point in time.

Anyway, I'll continue ignoring this aspect of trackers for now -- at least while I focus on effects.  For the time being my tracker uses only the ticks-per-row "speed" parameter.

Thanks
    -dZ.

[DZ-Jay]

I found the following information in the OpenMPT Wiki page.  OpenMPT is an open source music tracker that includes support for older formats, such as MOD, XM, IT, etc.

https://wiki.openmpt.org/Manual:_Song_Properties#Classic_Tempo_Mode

I imagine that the description of "Classic Tempo Mode" conforms to the way that old school trackers like FT2 handle tempo (Beats Per Minute) vs. speed (ticks per row).

     -dZ.