I get a runtime error but I can not find the problem. (It does not work on IOS even while it works on my chromebook)

[Ryank12]

[ABG]

I am surprised this works on a Chromebook.

Your use of a delay procedure is anathema to mobile devices.

Try a fast (30 ms) Clock Timer and a sheet music table for each song, with columns
note, remaining duration in ms
with current note playing in slot 1, updating item 1 each Timer cycle until it is ready to be removed and the next item pops down into slot 1.

Sample apps, none exactly matching your app but built on same ideas:

Morse

AI2 text to speech singing

Trying to get a pause in procedure execution

Here is a clock Timer based approach for an exercise routine, using deadline variables for each next event ... [blocks] [Capture] [Designer] exercise.aia (3.4 KB) [global Button1_deadline_ms] [global Button2_deadline_ms] [global Button3_deadline_ms] [when Button1 Click] [when Button2 Click] [when Button3 Click] [when Clock1 Timer] Clock1.Timer controls everything, by checking for expired deadlines and rescheduling them after initiating their events. For a lot of similar components, you can …

and also see

FAQ Section: Waiting and Timing

Async Procedure extension - kodular How to do something long running - Taifun How to run an accurate metronome Pause and Break in Loops Extension - Juan Antonio Why you can't wait in AI2 Event-Based programming in AI2 - FTurbak CCSCNE14-AI2-events-first-paper.pdf (432.1 KB) How to avoid using delay() in Arduino - JuanAntonio, docs.arduino.cc