HP41.org

the most detailed HP41 beep analysis I could find is there: https://www.hpcalc.org/details/7826
However, the duration of each tone is not clearly announced. Is it 0,28s?

? BEEP = .. ?
..
* TONE 7 = 629 Hz for 0,28s
* TONE 5 = 394 Hz for 0,28s
* TONE 8 = 788 Hz for 0,28s
* TONE 7 = 629 Hz for 0,28s
..

Any advice is welcome.

Multiple analysis were done over time in the PPC Journals.
Jeremy Smith's Synthetic Programming Quick Reference manual (hp41.org & hpcalc.org)
has a graph that shows the 128 possible tones, the associated note (frequency) and duration. (p.24)
Tone informations can also be found in William Wickes's, Synthetic Programming book and in Cary Reinstein's, HP-IL/HP-41 System Dictionary book.

See comments for XBEEP and XTONE in VASM listing, e.g. "Coconut VASM GFF.txt" on Warren's DVD.