Sekaiju, Frinika for MIDI Sequencing and Musescore for MIDI notation. For a free DAW (Digital Audio Workstation including MIDI, use Tracktion 5.

Sekaiju

Frinika

Musescore

Tracktion 5

Don't be afraid to take the time to learn a little of the bloat, perhaps what you are calling bloat are advanced features that can be usefull.

For Windows, I have always been happy with Voyetras' Digital Orchestrator (formerly Midi Orchestrator). It wasn't free, but it was a professionally developed suite from time where there wasn't any space for bloatware. It might be quite tricky to get hold of it and get it running nowadays, but checking whether I can do that would be my first choice if I had to come up with a sequencer.

I still have an Atari plus software which I use to play very old Cubase .ARR files. I sympathise with your problem to some extent, but I have also been using the more recent versions of Cubase for some years and haven't had any timing issues. Maybe you should consider whether your other equipment is causing latency. Possibly your arrangements are very big -- in that case it's hard for any software to cope perfectly.
I use an outboard interface and Roland hardware synths for the vast majority of my stuff, and my Mac Mini seems to run it all with no problems, as did my Vaio PC laptop a couple of years ago. I also record some tracks on an outboard recorder and import them.
The latest Cubase has an arrangement list feature that is like the one on the old Pro 24 for Atari, only better.
There is an inherent timing issue with software metronomes, but that exists on the Atari as well and is much less noticeable on my present system.

In general the problem is more related with the design of the computer motherboards than with the software itself.

It could happen the paradox that a 15 years old (or more) motherboard with an old OS like Windows 98SE, an old MIDI interface like an MQX32 and any old sequencer could have a much more better timing and timestamping that any of the new computers with Intel i7 or Xeon processors.

This old computers could access directly to the hardware instead of accesing to a virtualized abstraction layers, the cost was that when they fail it was a complete catastrophe and you lose all your work.

This is a problem of the HARDWARE design of the motherboards related with the packetized internal comunication of the data in the PCIe buses.

I have been using Passport's Master Tracks Pro for over twenty years now. It is the best and easiest stand alone sequencer application I have ever found.
I make tracks for 3 different bands and many people say the tracks sound very much like a real live band.
There is nothing it cannot do and do it easily.

Hello everybody here!

Stumbled into this blog just today: how incredibly refreshing to find other MIDI users looking for simple, straightforward MIDI editors/sequencers just as I do.

Sure enough, I also had a big love for the Atari ST (also owned a Falcon): everything was clear and solid with it. But, unbelievably, so many efforts have been wasted in order to turn a perfectly good musical system into a nightmare: innumerable software houses (many of which simply vanished after a few years) have tried to convince users into adopting their own crazy concoctions. Money, money, money...

Well, here's my 2 cents: there's been one really good sequencer/editor for the PC in the 2000's, namely Jazz++, which had many fantastic possibilities... without obliging anyone to even notice them!
It was my workhorse for years, way before the "Soundfont Era", and it's a real pity that nobody succeeded into perfecting a newer version; it does still run fine on Win$ 7 (haven't tried on Win$ 10).
Look around for Jazz++NT, the last official version; I haven't tried compiling it myself.

Another interesting (and actively maintained) program is SynthFont, which allows playing any MIDI track with a different Soundfont file. Sadly, it is rather slow and tricky as an editor...

And several years ago there was MidiSwing, a tiny JavaRunTime program which, at least, offered simple MIDIfile editing and playback with no hassle; it can still be found somewhere, but seems mostly abandoned by its original French developers.
No matter what Operating System you're using, once you have JavaRunTime installed you can run it -- I ran it under Puppy Linux without problems.

Now I'd like to test Sekaiju and Helio... Hints anyone?

All the best to everybody!

capoverde.

Anvil Studio seems to work okay for many people.

True, you can pay for various upgrades, but the basic program seems to be enough for many.

Sekaiju, as already mentioned, is another very capable package.

Nobody has mentioned MidiEditor yet. It is simple, cross-platform (Linux and Windows), open source, and GPL licensed.