Cakewalk by BandLab is free. It has a "music score screen" and a list view for entering MIDI events one at a time.
It does a lot more than you want, but the sequencing part has the essentials you're looking for.

Thanks, Eddie, I appreciate your help. I'm following up your suggestion but am unable to install Cakewalk. I have downloaded the BandLab Assistant and followed the instructions but I get no facility to install Cakewalk. I've raised a support ticket to resolve the issue but am stumped at the moment. Once I hear from them, I'll post here again to let you know how things are going.

Hmm, that's odd.

When you launch the BandLab Assistant do you see the "Library", "Sounds" and "Apps" tabs at the top of the window? If so, click on the "Apps" tab, then below "Cakewalk" click the "install" button.

If this doesn't help, hopefully BandLab support will get you going.

BandLab have responded and I have discovered something I hadn't realised. Several years ago, I bought "Music Creator 2" by Cakewalk and still have the original installation disk. I installed it but was still able to run my Atari setup so never used the MC2 software although it's still on my computer. Following BanLabs' instructions, I have their version installing - it seems I had to tick all the add-ons before clicking .

I'm now not sure if I'll have two versions of Cakewalk available and whether they will be identical or not. Once the installation is complete, I'll give it a run-through and see if it does the job.

Ideally, I would like to access the old "song" files the I created with Breakthru' but I suspect they'll be in an unusable format and I'll have to pursue the Atari emulator (STEEM) before I can use them. It looks like that will involve creating a disk image file to use within STEEM and that fills me with dread - it seems to require an internal floppy drive and my external (USB) drive will not work. That means buying and internal drive and, horror of horrors, delving into the guts of my computer to install it - I could end up with a busted PC!

As far as Cakewalk is concerned, would you be able/willing to help if I need assistance?

I'm not an expert with Cakewalk, but if you don't have an account at the Cakewalk forums you're welcome to post your questions here and I can try to help.

It gets weirder. When I fired up Cakewalk by BandLab, there was no facility to enter music on a Score sheet - the facility was greyed-out. However, when I ran Music Creator 2, there was a score sheet facility which looks like it might do the business. Over the weekend, I'm going to have to do some serious experimenting to get all my midi equipment linked up with the software and see if it works as I want. BandLab Support are still assisting with the greyed out Score sheet facility and look to be the helpful kind, so I hope to get that sorted out.

Hopefully, I can take things on from here and not trouble you any further. However, I do give you my thanks for directing my attention to Cakewalk. Wish me luck!

At a guess, you might not have created a MIDI track. You need to first create a MIDI track before you can open the staff view.

OK - that seems like it was the case - thanks. I have managed to enter some notes from my master keyboard that appear on the Staff page and can then make them play back on the keyboard. I have spoken to BandLab's support staff and have found them very helpful. I now need to know how to select the voices on my various sound modules/slave keyboards by midi messages so that I can step-entry some backing tracks and have them play on the appropriate voice.

BandLab have finally opened the official forum for Cakewalk.
New users can now sign up and join in the conversation.

Hi Eddie: I had to put everything on the back burner while I attended to real life for a spell. Anyway, I've persevered with Cakewalk and the BandLab support people are holding my hand. I'm hopeful that, now I'm back in circulation, I shall see a successful conclusion to my efforts. I thought you deserved this update for being so helpful to me.

Mike, that's good to hear. 🙂

Are you posting in the Cakewalk forum as well? The regulars there are also very helpful.