I am grateful to Hraban for his encouraging response, but though I could see it was related, it seems to me not quite what I seek.
The more I thought about the answer, I realised I had not explained my question in a precise manner.
I am retired, and produce a weekly A5 booklet from material with which my wife (a church minister), supplies to me. I call it a pulpit manuscript. It is the entire script for her service. Included are the numbers and first line of five hymns, that are different each week.
Until I gain a better understanding of ConTeXt, I shall continue to use LaTeX koma-script package for the weekly booklet. In order to make life easier for myself, I have created commands of my own.
One of these commands enables me to have a template which has five instances of \hymn{} {}. If I put with the first braces pair '387', and in the second pair, 'The Lord's my shepherd' --- when LaTeX koma-script outputs the PDF, 'Hymn 387' is in bold and 'The Lord's my shepherd' is italicised. For the next hymn, it would be a different number, and different first line, but it would auto-formatted the way I want.
That command is constructed in the preamble in the following way:
\newcommand{\hymn}[3][Hymn]{\addsec{\rlap{\textbf{#1 #2}}\hspace}{7em}{\normalfont\small\textit{#3} }}}
This places a specific gap between the hymn number and the first line as well. Not only does it format the section heading (\addsec) to have bold and italics (without bold), it formats the corresponding entry in the toc in exactly the same way.
How can I make a similar command for ConTeXt, please?