Maelz DX Pro is simple and beautiful metronome. In addition to basic functions of metronome, 1. Tuning Fork(A, B flat, C, E flat). 2. Rotatable Key-Circle(useful tool for writing score that is transpose key). Maelz DX Pro is ad-free paid version. Basic function is same as Maelz DX(It have ad, but free! ). We recommend you to buy this app after you try a free version.