f(Hz) = 440 * 2^(key-49)/12

"""
reference: https://iquanta.org/instruct/python ::: Piano: Frequencies of Notes ::: Stephen Lukacs, Ph.D. ©2023-03-22
"""
<page_scripts>
<style>
table.notes { width: 200px; }
table.notes td { padding: 2px 8px; }
table.notes tr:nth-child(12n+2) td { border: 2px solid gray; border-radius: 5px; }
table.notes tr:nth-child(12n+5) td { border: 2px solid pink; border-radius: 5px; }
</style>
</page_scripts>
from yatl.helpers import *
import plotly.graph_objects as go

BR = TAG['br/']
rtn = DIV()
if 1:
    html = { '':"&natural;", '-':"&natural;", '_':"&flat;", '^':"&sharp;", '#':"&sharp;" }
    octave = ['A', 'A#/B_', 'B', 'C', 'C#/D_', 'D', 'D#/E_', 'E', 'F', 'F#/G_', 'G', 'G#/A_']
    for i, o in enumerate(octave):
        xx = o.find('/')
        if (xx > -1):
            octave[i] = o[:xx]+"~"+'/<span class="flat">'+o[xx+1]+html["_"]+"</span>~"
        else:
            octave[i] = o+"~"
    Hz440 = lambda n: round(440.*(2**((n-49)/12.)), 5)
    Hz432 = lambda n: round(432.*(2**((n-49)/12.)), 5)
    nth_octave, ith_octave = 8, 3
    snth_octave = str(nth_octave)
    t = TABLE(TR(TH("key"), TH("note"), TH("f (Hz)"), TH("f Tesla (Hz)"),), _class="notes")
    for n in range(88, 0, -1):
        try:
            key = XML(octave[ith_octave].replace('~', snth_octave))
        except Exception as E:
            rtn.append(E)
        t.append(TR(TD(n), TD(key), TD(Hz440(n)), TD(Hz432(n))))
        ith_octave -= 1
        if (ith_octave < 0):
            ith_octave = 11
        if (ith_octave == 2):
            nth_octave -= 1
            snth_octave = str(nth_octave)
    rtn.append(DIV(t, _style="float:left;"))
    fig = go.Figure()
    fig.add_trace(go.Scatter(x=[ i for i in range(1, 89) ], y=[ Hz432(i) for i in range(1, 89) ], mode='markers', name="tesla", marker=go.scatter.Marker(color="DarkGray")))
    fig.add_trace(go.Scatter(x=[ i for i in range(1, 89) ], y=[ Hz440(i) for i in range(1, 89) ], mode='markers', name="notes", marker=go.scatter.Marker(color="Black")))
    fig.update_layout(xaxis=go.XAxis(title="key"), yaxis=go.YAxis(title="Frequency (Hz)", anchor='x', side='left'))
    fig.update_layout(title_text="Piano Frequency Response per Key", height=1050, margin=go.layout.Margin(l=25, r=25, b=60, t=60, pad=0), plot_bgcolor="#f5f5f5", paper_bgcolor="White")
    html = fig.to_html()
    rtn.append(CAT(DIV(H1(XML("f(Hz) = 440 * 2<sup>(key-49)/12</sup>")), BR(), XML(html[html.find('<div>'):html.rfind('</div>')+6].replace('<div>', '<div id="plotly">')), _style="float:left; margin: 0px 10px; width: 75%; border: 0px solid black; border-radius: 4px;"), DIV(_style="float:none; clear:both;")))