Looking around at other people's solutions - I found they'd return a large value on the first tap if left alone for a while, so I made this little tap tempo with a timeout that resets it.
TapTempo_timeout.pd
I like its immediacy so haven't added averaging or anything, open to improvements!

@ddw_music Amazing, thanks so much - I'll try building in SuperCollider

@jameslo Thanks for replying after such a long time, it seems I wasn't asking the right question in the first place.

@ddw_music Thank you for taking the time to write such a detailed response, I think I finally understand.

So what I actually mean is I want to minimise the error in a BPM change of two semitones, and find the start and end values where it's lowest, even if they're both fractions. I think?

@jameslo Two years later but hey - ratio was probably the wrong word to use, sorry. I updated the patch so it starts with whole numbers, hopefully making it easier to understand:

bpmcalculator2.pd

So good ones would be:
69 BPM gives 61.472
59 BPM gives 52.563

A bad one would be:
77 BPM gives 68.5992

It's for a studio project where I have to pitch and slow everything down 2 semitones. The starting point isn't so important, but the nearer to a whole number it is the better precision there is with keeping everything on the grid.
So, starting with the smallest number of decimal places and ending with the smallest number of decimal places is preferable, does that make sense?

@jameslo Am I right in thinking you put the dll, lib or vst3 (renamed?) in the folder with the patch (text file and so on) for Windows? ...and then add the folder to your plugins directory?
Rather than editing a renamed package's contents and relocating it as on Mac?

It's implied in the wiki but it seems to just stop at stage 6 for Windows/Linux when the Mac instructions continue, which I guess could confuse people.

Yes please!

This is immense! Thanks a lot

Have you had a look at the patch I posted? I think that’s what I did!

I suppose I’m looking for the most ‘harmonic’ ratios. Would be useful going forward too I suppose when working with anharmonic spectral stuff.

Thanks - but the maths help I need is how to find ratios between the bpm changes.

BPMcalculator.pd

Messing about with this simple patch to calculate BPM change when something is slowed down two semitones and I wondered - how would I find the most whole numbered/least amount of decimal places change/ratio?

I think this is probably a basic maths question, but I have no clue how to approach it. Thanks!

@whale-av Thanks so much = exactly what I needed!

I have 124 receive~ instances, is there a way to create a random send~ without creating 124 of them?
Thanks!

@Pierre-Guillot Yes of course! Linking to this thread is fine, sorry for the slow reply.

It was down for a while, but now back up here

Would 500ms make it doom? Ha

I added - Reverb, stereo position and counterpoint rules - otherwise it's as per the original algorithm. They're labelled, so you could just cut these out if you wanted.

I've not tried any other scales and rules, maybe it could map 3 chromatic octaves to the 26 letters of the alphabet instead? I did wonder about using something traditionally metal sounding like a minor scale or phrygian mode but then how to 26÷8.

Kangtaum.zip
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Kangtaum is an attempt at a real-time implementation of the text-to-(Black Metal)music algorithm proposed by Dave Tremblay.

The algorithm was intended for use with Tolkien’s writing; this version will produce a microtonal scriptophonic ‘metal’ composition from any text file that is input. The default is the poem She Bomber by Eliza Gregory, the text currently being converted is output to the Pd window.
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Here's how it works:

·The octave is divided in 26 equal steps (26 microtones, one for each letter).

·The ordering of the letters, from low to high, is:
E-O-V-I-Q-C-F-A-J-Z-P-H-B-Y-S-R-K-D-T-L-X-M-N-G-W-U based on their frequency of use in the sample text (Tolkein).

·One letter represents a duration of 1/8th note.

·One comma, parenthesis or semicolon is a ‘tie’ to the last note played (1/8th duration normally) is continued for a ¼.

·A full stop, colon, exclamation or question mark is a pause of 1/8th measure.

·There are three transcription tracks:

1. The melody: It is each letter and punctuation in the text played one after the other.
2. The chords: A chord lasts as long as a word in the melody (for example, a three-letter word will last 3 eights notes, and a nine-letter word will last 9 eights). It's comprised of all the different notes/letters of the word played at once.
3. The bass: The bass track or chord root consists of the first letter of each word played for the duration of the word. For example, the words THAN and NATH have the same notes and length, but the root and melody of the chords will be different).

·Reverberation for the composition is inversely proportional to the size of the current text chunk or sentence being converted into music. The bigger the chunk, the smaller the virtual space.

·The stereo position of the melody is controlled by the length of the word currently being sonified.

·A counterpoint line is generated from a reordering of the current word/chord’s notes from low to high, which is arpeggiated. The balance between melody and counterpoint is controlled by word length. The longer the word the more melody is present.

This isn't a finished patch, i've kind of reached a dead end with it so thought I'd open it up and see if any one else would like to chip in. I'm really interested in developing the synthesis side of things and making it sound more METAL I suppose.
If nothing else, hopefully some of the list processing is useful to someone working to convert text to music. Many thanks to those on the forum that helped me work some of it out or provide solutions.

This is a video of a slightly earlier version:

Here is an example of Dave's music produced with the original algorithm.

Simplest overdrive/distortion/fuzz type effect is multiplying a signal and then clipping it.

adc~
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[*~ 5]
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[clip~ -0.2 0.2]
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dac~

@formuls This is great man - thanks a lot for sharing.