I wanted to know if there is a limit to how many patterns you can have in a song. I don't think I will ever have an issue of not having enough patterns to be able to finish a song and I have only ever used up to 15 patterns in one song. I just wanted to know if there is a limit and what that limit is.
That depends on the song format. Some of the limits can be found here: https://wiki.openmpt.org/Manual:_Saving_and_exporting#Compatibility_Export
What about Impulse Tracker for example, how many patterns are you allowed to have using that format?
IT supports about 200 patterns. MPTM supports the most patterns (4000).
Thanks for the info. I don't ever see anyone really needing to use even 50 patterns for a single song, but 4000 patterns is quite a lot for MPTM.
It's great for music that uses a lot higher precision with much faster tempo, where several patterns represent a bar rather than just one.
There are also reasons for putting several songs into a single file, e.g. for game soundtracks, and that can require several hundreds of patterns, too.
So if you have multiple songs in one file can you switch between each individual song or do you have to start from the beginning of the first song in that file?
Do you mean in OpenMPT or when using such a song in a game? When using MPTM's multi-sequence feature, you can put each song in its own order list (sequence) and easily listen to the songs separately export all of them into separate streaming files, but for other formats you will have to point the pattern editor at the correct starting position in the order list to listen to individual songs. Audio players like XMPlay can automatically detect those starting positions and let you play specific subsongs without having to listen to the whole file but that's entirely application-specific.
I mean't in OPENMPT, also is there a way to add more channel effects slots to the pattern editor?
No, there isn't: https://forum.openmpt.org/index.php?topic=5517.0