Music Speed Changer has a setting in the editor that will join the Tempo and Pitch into a single parameter called Rate. Rate is a proportional frequency and tempo shift used for natural rate change in music.
See here for a step by step on joining pitch and tempo into rate in the app
Calculating a change in rate to increase or decrease frequency is fairly simple. You take your desired output frequency and divide by the starting frequency and multiply by 100 to turn the resulting rate into a percentage. You can simply use the calculator at the top of the page and tap copy to then easily paste your result into the app.
If you are increasing music rate to make nightcore out of your favorite tracks, see here for tips on making nightcore music: