This app was mentioned in 11 comments, with an average of 1.18 upvotes
I sorta have a suggestion for you, even though it barely meets your criteria.
Ok, so here's the deal: it does not have a ~~~great~~~ pretty UI, it is not open source, I know zilch about the developer, & even the app's icon is ugly as sin. I'm know there are audio editors out there that have most or even all of these aspects, but I assure you they will not come close to matching this app's functionality. The Play Store has hundreds if not thousands of audio editors & ringtone makers, most of which are simply re-skinned versions of the same shitty UI, while the rest are either extremely barebones and/or super spammy, permission hungry piles of poo.
Trust me, I've spent an outrageous amount of time scouring the Play Store, F-Droid, & XDA for an audio editor that has even a fraction of Lexis's functionality. It is permission friendly & does its job very well, which is why I felt it worthwhile to recommend it despite lacking the things you asked for. Unfortunately, quality audio editors are even more hard to come by than quality video editors in the Android marketplace.
There is a one-time semi steep IAP of $6 to unlock the the ability to save files as mp3 (saving in wav, flac, & wma are available in free version) & possibly to remove ads, but to be honest I can't remember if there really were any since I paid for pro almost immediately after all the aggravation I've experienced from searching & being disappointed in so many others.
Hello! Sorry I slept yesterday. I'll tell you everything that I do.
Download: Lexis Audio Editor - from Play Store (https://play.google.com/store/apps/details?id=com.pamsys.lexisaudioeditor)
Download: T2S (this one: https://play.google.com/store/apps/details?id=hesoft.T2S)
Then write your affirmations on T2S (keep the pitch and rate in normal speed: 1 - it'll be that by default)
→ write affirmations in present continuous tense because I write mine in all present continuous tense only and sometimes add a few present simple tense if I want to.. my Belly Fat Reduction with which I lost 6 inches contains only present continuous tense.
• For example, my abdomen is burning fat right now.
• Eg: my waist fat is burning. (I don't write "losing" because I don't have complete faith in it. I feel like once we lose, it'll come back, haha. That's why. But write it if you believe the word 'lose' works for you!)
Lexis Audio Editor is one that I was recommended long ago. Never ended up using it, but it may be worth a shot. the IAP is around $7 or so for mp3 export.
You'll need a better mic, but try this software: https://play.google.com/store/apps/details?id=com.pamsys.lexisaudioeditor&hl=en\_US&gl=US
this app can do it - https://play.google.com/store/apps/details?id=com.pamsys.lexisaudioeditor
I've had good results using Lexis Audio Editor
https://play.google.com/store/apps/details?id=com.pamsys.lexisaudioeditor
I recommend Lexis audio editor
Just found this. Seems like it could work...
https://play.google.com/store/apps/details?id=com.pamsys.lexisaudioeditor
Check this one out.
https://play.google.com/store/apps/details?id=com.pamsys.lexisaudioeditor
Just downloaded so I can't say it work or not yet.
Something like this? https://play.google.com/store/apps/details?id=com.pamsys.lexisaudioeditor&hl=en