Probabilistic Denoising Diffusion models have emerged as simple yet very powerful generative models. Diffusion models unlike other generative models do not suffer from mode collapse nor require a discriminator to generate high quality samples. In this paper, we propose a diffusion model that uses a binomial prior distribution to generate piano-rolls. The paper also proposes an efficient method to train the model and generate samples. The generated music has coherence at time scales up to the length of the training piano-roll segments. We show how such a model is conditioned on the input and can be used to harmonize a given melody, complete an incomplete piano-roll or generate a variation of a given piece. The code is shared publicly to encourage the use and development of the method by the community.